diff --git a/app/main/forms.py b/app/main/forms.py
index 70274168e..c8c76c816 100644
--- a/app/main/forms.py
+++ b/app/main/forms.py
@@ -1942,13 +1942,7 @@ class CallbackForm(StripWhitespaceForm):
 
 
 class SMSPrefixForm(StripWhitespaceForm):
-    enabled = RadioField(
-        '',
-        choices=[
-            ('on', 'On'),
-            ('off', 'Off'),
-        ],
-    )
+    enabled = OnOffField('')  # label is assigned on instantiation
 
 
 def get_placeholder_form_instance(
diff --git a/app/main/views/service_settings.py b/app/main/views/service_settings.py
index 3d690bf2f..2fbd12b23 100644
--- a/app/main/views/service_settings.py
+++ b/app/main/views/service_settings.py
@@ -630,15 +630,13 @@ def service_set_inbound_number(service_id):
 @user_has_permissions('manage_service')
 def service_set_sms_prefix(service_id):
 
-    form = SMSPrefixForm(enabled=(
-        'on' if current_service.prefix_sms else 'off'
-    ))
+    form = SMSPrefixForm(enabled=current_service.prefix_sms)
 
     form.enabled.label.text = 'Start all text messages with ‘{}:’'.format(current_service.name)
 
     if form.validate_on_submit():
         current_service.update(
-            prefix_sms=(form.enabled.data == 'on')
+            prefix_sms=form.enabled.data
         )
         return redirect(url_for('.service_settings', service_id=service_id))
 
diff --git a/app/templates/views/service-settings/sms-prefix.html b/app/templates/views/service-settings/sms-prefix.html
index 02b6daa04..718906a98 100644
--- a/app/templates/views/service-settings/sms-prefix.html
+++ b/app/templates/views/service-settings/sms-prefix.html
@@ -1,5 +1,4 @@
 {% extends "withnav_template.html" %}
-{% from "components/radios.html" import radios %}
 {% from "components/page-header.html" import page_header %}
 {% from "components/page-footer.html" import page_footer %}
 {% from "components/form.html" import form_wrapper %}
@@ -16,7 +15,7 @@
   ) }}
 
   {% call form_wrapper() %}
-    {{ radios(form.enabled) }}
+    {{ form.enabled }}
     {{ page_footer('Save') }}
   {% endcall %}
 
diff --git a/tests/app/main/views/test_service_settings.py b/tests/app/main/views/test_service_settings.py
index 496909185..8029f0add 100644
--- a/tests/app/main/views/test_service_settings.py
+++ b/tests/app/main/views/test_service_settings.py
@@ -4450,22 +4450,21 @@ def test_show_sms_prefixing_setting_page(
     )
     radios = page.select('input[type=radio]')
     assert len(radios) == 2
-    assert radios[0]['value'] == 'on'
+    assert radios[0]['value'] == 'True'
     assert radios[0]['checked'] == ''
-    assert radios[1]['value'] == 'off'
+    assert radios[1]['value'] == 'False'
     with pytest.raises(KeyError):
         assert radios[1]['checked']
 
 
-@pytest.mark.parametrize('post_value, expected_api_argument', [
-    ('on', True),
-    ('off', False),
+@pytest.mark.parametrize('post_value', [
+    True,
+    False,
 ])
 def test_updates_sms_prefixing(
     client_request,
     mock_update_service,
     post_value,
-    expected_api_argument,
 ):
     client_request.post(
         'main.service_set_sms_prefix', service_id=SERVICE_ONE_ID,
@@ -4477,7 +4476,7 @@ def test_updates_sms_prefixing(
     )
     mock_update_service.assert_called_once_with(
         SERVICE_ONE_ID,
-        prefix_sms=expected_api_argument,
+        prefix_sms=post_value,
     )