why did my Nokia Lumia 635 stop sending and receiving text messages

[mcclerren420]

My Nokia Lumia 635 was purchased unlocked and I set it up with straight talk, it worked great for 2 months and I noticed I couldn't send my fiancee text messages but she could send them to me and I could messages everyone else.my service expired and I renewed the service and asked straight talk if they could fix the texting problem, now I can't send or receive text messages from anyone. I did a hard reset and redid all the apn,port,URL settings for straight talk as I did when I first got the phone and still nothing. Someone said to replace the SIM card. Any ideas or solutions would be greatly appreciated