diff --git a/app/delivery/send_to_providers.py b/app/delivery/send_to_providers.py
index c0d32bf86..4f811de22 100644
--- a/app/delivery/send_to_providers.py
+++ b/app/delivery/send_to_providers.py
@@ -10,6 +10,7 @@
 from app.dao.email_branding_dao import dao_get_email_branding_by_id
 from app.dao.notifications_dao import dao_update_notification
 from app.dao.provider_details_dao import get_provider_details_by_notification_type
+from app.dao.service_sms_sender_dao import dao_get_sms_senders_by_service_id
 from app.enums import BrandType, KeyType, NotificationStatus, NotificationType
 from app.exceptions import NotificationTechnicalFailureException
 from app.serialised_models import SerialisedService, SerialisedTemplate
@@ -101,6 +102,13 @@ def send_sms_to_provider(notification):
                     raise Exception(
                         f"The recipient for (Service ID: {si}; Job ID: {ji}; Job Row Number {jrn} was not found."
                     )
+
+                sender_numbers = get_sender_numbers(notification)
+                if notification.reply_to_text not in sender_numbers:
+                    raise ValueError(
+                        f"{notification.reply_to_text} not in {sender_numbers} #notify-admin-1701"
+                    )
+
                 send_sms_kwargs = {
                     "to": recipient,
                     "content": str(template),
@@ -130,6 +138,14 @@ def send_sms_to_provider(notification):
     return message_id
 
 
+def get_sender_numbers(notification):
+    possible_senders = dao_get_sms_senders_by_service_id(notification.service_id)
+    sender_numbers = []
+    for possible_sender in possible_senders:
+        sender_numbers.append(possible_sender.sms_sender)
+    return sender_numbers
+
+
 def send_email_to_provider(notification):
     # Someone needs an email, possibly new registration
     recipient = redis_store.get(f"email-address-{notification.id}")
diff --git a/tests/app/delivery/test_send_to_providers.py b/tests/app/delivery/test_send_to_providers.py
index af65dd766..7f16a799a 100644
--- a/tests/app/delivery/test_send_to_providers.py
+++ b/tests/app/delivery/test_send_to_providers.py
@@ -318,6 +318,9 @@ def test_should_send_sms_with_downgraded_content(notify_db_session, mocker):
     # é, o, and u are in GSM.
     # ī, grapes, tabs, zero width space and ellipsis are not
     # ó isn't in GSM, but it is in the welsh alphabet so will still be sent
+    mocker.patch(
+        "app.delivery.send_to_providers.get_sender_numbers", return_value=["testing"]
+    )
     msg = "a é ī o u 🍇 foo\tbar\u200bbaz((misc))…"
     placeholder = "∆∆∆abc"
     gsm_message = "?ódz Housing Service: a é i o u ? foo barbaz???abc..."
@@ -327,6 +330,7 @@ def test_should_send_sms_with_downgraded_content(notify_db_session, mocker):
         template=template,
     )
     db_notification.personalisation = {"misc": placeholder}
+    db_notification.reply_to_text = 'testing'
 
     mocker.patch("app.aws_sns_client.send_sms")
 
@@ -609,11 +613,16 @@ def __update_notification(notification_to_update, research_mode, expected_status
 def test_should_update_billable_units_and_status_according_to_research_mode_and_key_type(
     sample_template, mocker, research_mode, key_type, billable_units, expected_status
 ):
+
+    mocker.patch(
+        "app.delivery.send_to_providers.get_sender_numbers", return_value=["testing"]
+    )
     notification = create_notification(
         template=sample_template,
         billable_units=0,
         status=NotificationStatus.CREATED,
         key_type=key_type,
+        reply_to_text='testing',
     )
     mocker.patch("app.aws_sns_client.send_sms")
     mocker.patch(
@@ -771,9 +780,13 @@ def test_send_email_to_provider_uses_reply_to_from_notification(
 
 
 def test_send_sms_to_provider_should_use_normalised_to(mocker, client, sample_template):
+
+    mocker.patch(
+        "app.delivery.send_to_providers.get_sender_numbers", return_value=["testing"]
+    )
     send_mock = mocker.patch("app.aws_sns_client.send_sms")
     notification = create_notification(
-        template=sample_template, to_field="+12028675309", normalised_to="2028675309"
+        template=sample_template, to_field="+12028675309", normalised_to="2028675309", reply_to_text='testing'
     )
 
     mock_s3 = mocker.patch("app.delivery.send_to_providers.get_phone_number_from_s3")
@@ -826,6 +839,10 @@ def test_send_email_to_provider_should_user_normalised_to(
 def test_send_sms_to_provider_should_return_template_if_found_in_redis(
     mocker, client, sample_template
 ):
+
+    mocker.patch(
+        "app.delivery.send_to_providers.get_sender_numbers", return_value=["testing"]
+    )
     from app.schemas import service_schema, template_schema
 
     service_dict = service_schema.dump(sample_template.service)
@@ -845,7 +862,7 @@ def test_send_sms_to_provider_should_return_template_if_found_in_redis(
 
     send_mock = mocker.patch("app.aws_sns_client.send_sms")
     notification = create_notification(
-        template=sample_template, to_field="+447700900855", normalised_to="447700900855"
+        template=sample_template, to_field="+447700900855", normalised_to="447700900855", reply_to_text='testing'
     )
 
     mock_s3 = mocker.patch("app.delivery.send_to_providers.get_phone_number_from_s3")