diff --git a/sinch/core/clients/sinch_client_configuration.py b/sinch/core/clients/sinch_client_configuration.py
index 59e3712..2338749 100644
--- a/sinch/core/clients/sinch_client_configuration.py
+++ b/sinch/core/clients/sinch_client_configuration.py
@@ -45,7 +45,7 @@ def __init__(
         self._conversation_domain = ".conversation.api.sinch.com"
         self._sms_region = "us"
         self._sms_domain = "zt.{}.sms.api.sinch.com"
-        self._sms_domain_with_service_plan_id = "sms.api.sinch.com"
+        self._sms_domain_with_service_plan_id = "{}.sms.api.sinch.com"
         self._sms_authentication = HTTPAuthentication.OAUTH.value
         self._templates_region = "eu"
         self._templates_domain = ".template.api.sinch.com"
diff --git a/tests/unit/test_configuration.py b/tests/unit/test_configuration.py
index fb83355..5a52fe8 100644
--- a/tests/unit/test_configuration.py
+++ b/tests/unit/test_configuration.py
@@ -26,6 +26,13 @@ def test_set_sms_region_property_and_check_that_sms_origin_was_updated(sinch_cli
     assert "irritating" in sinch_client_sync.configuration.sms_origin
 
 
+def test_set_sms_region_with_service_plan_id_property_and_check_that_sms_origin_was_updated(sinch_client_sync):
+    sinch_client_sync.configuration.sms_region_with_service_plan_id = (
+        "Herring"
+    )
+    assert sinch_client_sync.configuration._sms_origin_with_service_plan_id.startswith("Herring")
+
+
 def test_set_sms_domain_property_and_check_that_sms_origin_was_updated(sinch_client_sync):
     sinch_client_sync.configuration.sms_region = (
         "We interrupt this program to annoy you"