Since 2015-08-04 19:55:00 UTC T-Mobile USA have been experiencing an issue with their SMS service.
As a result of this issue, a portion of MO SMS messages from and standard rate MT SMS messages sent to subscribers on the affected carrier are currently being delayed.
MO SMS messages are being queued by the carrier and MT SMS messages are being queued on the SMS gateway for delivery once this issue has been resolved.
The carrier are aware of this issue and are working to resolve it as soon as possible. There is currently no estimated time to resolution, however we will issue an update as soon as more information becomes available.