Text messages

[Norma Hobgood]

I have a galaxy s3 and so does my sister . I am with tmobile and she is ATT. for some reason she can't get my text messages,just a blank screen.i get her messages fine.my phone is the only phone she has problems with. Any advice?

 

[B. Diddy]

Did you used to have an iPhone? If so, did you make sure to completely deactivate iMessage before switching to Android?