My calls are not going through likewise text messages

I can't make calls pr send text messages with my line even when I have airtime but I recieve messages

i know its niot my NIN cause i've done that a couple months ago, and network comes onn sometimes whenever there is network issues in my area, and then stops working later...

I bought a phone for my MTN line, I can receive calls, text messages and can also send text messages. However, I cannot call out. What should I do? I am in the US currently...