Originally Posted by ajm
It doesn't have anything to do with your phone or T-Mobile.
Sprint somehow thinks your phone is a landline or is not SMS-capable. Many providers now recognize when a destination is a landline and offer to translate the message into voice (it probably costs him money when they do this)
If you can receive text messages from other people then your friend should contact Sprint and report the problem.
Agreed - This is sprints problem. It also stems from a disconnect between carriers. Look for an article online called "SMS Disconnect". It will detail how all the carriers have had problems interrelating in the past.