Why can't I receive texts unless I am on the phone?

[AC Question]

I cannot recieve texts unless I am on the phone.

I have not been able to receive any texts unless I am in a call. I can send texts but not receive them. I have restarted my phone a bunch of times, and have taken out the battery. I have been using a texting app for a year, but I uninstalled it and I am still having the same problem.