Not able to receive sms(Text messages) - "providerResponse": "Message has been accepted by phone"

Hello, I am trying to send transactional sms (text messages) from SNS - 10DLC to T-Mobile US cell phone, and I can see from the CloudWatch that the messages have been accepted by the phone ("providerResponse": "Message has been accepted by phone"), however the messages are not delivered. Our customers don't receive these "accepted" messages on their phones. Also AWS charge me for these accepted but not delivered SMS, it's not fair.

Please assist.