Why can't I text to some numbers?

[iMore Question]

I receive texts from some people and not from others, I have iPhone 6 and AT&T. AT&T says it is an issue with my phone

 

[SwitchBeach]

Is this a problem with sending or receiving texts? You thread title says one thing and your post says something different.

Please provide more details on the "numbers" you cannot receive from.
What troubleshooting have you tried? Rebooting the phone? Resetting the Network connection in the Settings menu? Something else?