diff --git a/app/inbound_number/rest.py b/app/inbound_number/rest.py
index becaf21fc..24b2445c2 100644
--- a/app/inbound_number/rest.py
+++ b/app/inbound_number/rest.py
@@ -36,6 +36,8 @@ def post_allocate_inbound_number(service_id):
     if inbound_number:
         if not inbound_number.active:
             dao_set_inbound_number_active_flag(service_id, active=True)
+            service = dao_fetch_service_by_id(service_id)
+            insert_or_update_service_sms_sender(service, inbound_number.number, inbound_number.id)
             return jsonify(), 204
         else:
             return jsonify(), 200
diff --git a/app/models.py b/app/models.py
index a4743b491..a5da33951 100644
--- a/app/models.py
+++ b/app/models.py
@@ -253,21 +253,19 @@ class Service(db.Model, Versioned):
         if self.inbound_number and self.inbound_number.active:
             return self.inbound_number.number
         else:
-            return self.sms_sender
+            return self.get_default_sms_sender()
+
+    def get_default_sms_sender(self):
+        default_sms_sender = [x for x in self.service_sms_senders if x.is_default]
+        return default_sms_sender[0].sms_sender
 
     def get_default_reply_to_email_address(self):
         default_reply_to = [x for x in self.reply_to_email_addresses if x.is_default]
-        if len(default_reply_to) > 1:
-            raise Exception("There should only ever be one default")
-        else:
-            return default_reply_to[0].email_address if default_reply_to else None
+        return default_reply_to[0].email_address if default_reply_to else None
 
     def get_default_letter_contact(self):
         default_letter_contact = [x for x in self.letter_contacts if x.is_default]
-        if len(default_letter_contact) > 1:
-            raise Exception("There should only ever be one default")
-        else:
-            return default_letter_contact[0].contact_block if default_letter_contact else None
+        return default_letter_contact[0].contact_block if default_letter_contact else None
 
 
 class InboundNumber(db.Model):
@@ -306,7 +304,7 @@ class ServiceSmsSender(db.Model):
     id = db.Column(UUID(as_uuid=True), primary_key=True, default=uuid.uuid4)
     sms_sender = db.Column(db.String(11), nullable=False)
     service_id = db.Column(UUID(as_uuid=True), db.ForeignKey('services.id'), unique=True, index=True, nullable=False)
-    service = db.relationship(Service, backref=db.backref("service_sms_senders", uselist=False))
+    service = db.relationship(Service, backref=db.backref("service_sms_senders", uselist=True))
     is_default = db.Column(db.Boolean, nullable=False, default=True)
     inbound_number_id = db.Column(UUID(as_uuid=True), db.ForeignKey('inbound_numbers.id'),
                                   unique=True, index=True, nullable=True)
@@ -1030,7 +1028,7 @@ class Notification(db.Model):
             return NOTIFICATION_STATUS_LETTER_ACCEPTED
         else:
             # Currently can only be technical-failure
-            return status
+            return self.status
 
     def serialize_for_csv(self):
         created_at_in_bst = convert_utc_to_bst(self.created_at)
diff --git a/app/schemas.py b/app/schemas.py
index 38799baa2..8ce2e5ed5 100644
--- a/app/schemas.py
+++ b/app/schemas.py
@@ -183,6 +183,7 @@ class ServiceSchema(BaseSchema):
     permissions = fields.Method("service_permissions")
     override_flag = False
     reply_to_email_address = fields.Method(method_name="get_reply_to_email_address")
+    sms_sender = fields.Method(method_name="get_sms_sender")
     letter_contact_block = fields.Method(method_name="get_letter_contact")
 
     def get_free_sms_fragment_limit(selfs, service):
@@ -194,6 +195,9 @@ class ServiceSchema(BaseSchema):
     def get_reply_to_email_address(self, service):
         return service.get_default_reply_to_email_address()
 
+    def get_sms_sender(self, service):
+        return service.get_default_sms_sender()
+
     def get_letter_contact(self, service):
         return service.get_default_letter_contact()
 
diff --git a/tests/app/celery/test_ftp_update_tasks.py b/tests/app/celery/test_ftp_update_tasks.py
index 05680d32b..dc96ac91d 100644
--- a/tests/app/celery/test_ftp_update_tasks.py
+++ b/tests/app/celery/test_ftp_update_tasks.py
@@ -95,8 +95,8 @@ def test_update_letter_notifications_to_sent_to_dvla_updates_based_on_notificati
     client,
     sample_letter_template
 ):
-    first = create_notification(sample_letter_template)
-    second = create_notification(sample_letter_template)
+    first = create_notification(sample_letter_template, reference='first ref')
+    second = create_notification(sample_letter_template, reference='second ref')
 
     dt = datetime.utcnow()
     with freeze_time(dt):
@@ -113,8 +113,8 @@ def test_update_letter_notifications_to_error_updates_based_on_notification_refe
     client,
     sample_letter_template
 ):
-    first = create_notification(sample_letter_template)
-    second = create_notification(sample_letter_template)
+    first = create_notification(sample_letter_template, reference='first ref')
+    second = create_notification(sample_letter_template, reference='second ref')
 
     dt = datetime.utcnow()
     with freeze_time(dt):
diff --git a/tests/app/db.py b/tests/app/db.py
index b3b6ba61c..dfa3f6a07 100644
--- a/tests/app/db.py
+++ b/tests/app/db.py
@@ -28,8 +28,7 @@ from app.models import (
     KEY_TYPE_NORMAL,
     ServiceInboundApi,
     ServiceEmailReplyTo,
-    ServiceLetterContact
-)
+    ServiceLetterContact, ServiceSmsSender)
 from app.dao.users_dao import save_model_user
 from app.dao.notifications_dao import dao_create_notification, dao_created_scheduled_notification
 from app.dao.templates_dao import dao_create_template
@@ -71,7 +70,7 @@ def create_service(
         message_limit=1000,
         restricted=restricted,
         email_from=service_name.lower().replace(' ', '.'),
-        created_by=user or create_user(),
+        created_by=user or create_user(email='{}@digital.cabinet-office.gov.uk'.format(uuid.uuid4())),
         sms_sender=sms_sender,
     )
 
@@ -143,9 +142,6 @@ def create_notification(
         if not api_key:
             api_key = create_api_key(template.service, key_type=key_type)
 
-    if template.template_type == LETTER_TYPE and reference is None:
-        reference = create_random_identifier()
-
     data = {
         'id': uuid.uuid4(),
         'to': to_field,
@@ -354,6 +350,24 @@ def create_reply_to_email(
     return reply_to
 
 
+def create_service_sms_sender(
+    service,
+    sms_sender,
+    is_default=True
+):
+    data = {
+        'service_id': service.id,
+        'sms_sender': sms_sender,
+        'is_default': is_default,
+    }
+    service_sms_sender = ServiceSmsSender(**data)
+
+    db.session.add(service_sms_sender)
+    db.session.commit()
+
+    return service_sms_sender
+
+
 def create_letter_contact(
     service,
     contact_block,
diff --git a/tests/app/delivery/test_send_to_providers.py b/tests/app/delivery/test_send_to_providers.py
index c88b7f380..30ca1e876 100644
--- a/tests/app/delivery/test_send_to_providers.py
+++ b/tests/app/delivery/test_send_to_providers.py
@@ -271,15 +271,14 @@ def test_should_not_send_to_provider_when_status_is_not_created(
 
 
 def test_should_send_sms_sender_from_service_if_present(
-        sample_service,
-        sample_template,
+        notify_db_session,
         mocker):
-    db_notification = create_notification(template=sample_template,
+    service = create_service(sms_sender='elevenchars')
+    template = create_template(service=service)
+    db_notification = create_notification(template=template,
                                           to_field="+447234123123",
                                           status='created')
 
-    sample_service.sms_sender = 'elevenchars'
-
     mocker.patch('app.mmg_client.send_sms')
     mocker.patch('app.delivery.send_to_providers.create_initial_notification_statistic_tasks')
 
@@ -289,9 +288,9 @@ def test_should_send_sms_sender_from_service_if_present(
 
     mmg_client.send_sms.assert_called_once_with(
         to=validate_and_format_phone_number("+447234123123"),
-        content="This is a template:\nwith a newline",
+        content="Dear Sir/Madam, Hello. Yours Truly, The Government.",
         reference=str(db_notification.id),
-        sender=sample_service.sms_sender
+        sender=service.sms_sender
     )
 
 
@@ -656,16 +655,16 @@ def test_should_set_international_phone_number_to_sent_status(
     ('testing', 'testing', 'Sample service: bar'),
 ])
 def test_should_handle_sms_sender_and_prefix_message(
-    sample_service,
     mocker,
     sms_sender,
     expected_sender,
-    expected_content
+    expected_content,
+    notify_db_session
 ):
     mocker.patch('app.mmg_client.send_sms')
     mocker.patch('app.delivery.send_to_providers.create_initial_notification_statistic_tasks')
-    sample_service.sms_sender = sms_sender
-    template = create_template(sample_service, content='bar')
+    service = create_service(sms_sender=sms_sender)
+    template = create_template(service, content='bar')
     notification = create_notification(template)
 
     send_to_providers.send_sms_to_provider(notification)
diff --git a/tests/app/test_model.py b/tests/app/test_model.py
index 03f3fb146..a1bc1e343 100644
--- a/tests/app/test_model.py
+++ b/tests/app/test_model.py
@@ -26,6 +26,7 @@ from tests.app.db import (
     create_service,
     create_inbound_number,
     create_reply_to_email,
+    create_service_sms_sender,
     create_letter_contact
 )
 from tests.conftest import set_config
@@ -274,3 +275,8 @@ def test_service_get_default_contact_letter(sample_service):
     create_letter_contact(service=sample_service, contact_block='London,\nNW1A 1AA')
 
     assert sample_service.get_default_letter_contact() == 'London,\nNW1A 1AA'
+
+
+def test_service_get_default_sms_sender(notify_db_session):
+    service = create_service(sms_sender='new_value')
+    assert service.get_default_sms_sender() == 'new_value'