Why does it says my the numbers I dial doesn’t exist

Why can't I do anything with my sim card and I can't even answer call or make calls also or even to receive a text message and if I write down my number it shows wrong number

How to solve this problem. Your call is being forwarded. The number you have called does not exist when people call my android phone

When people call me it says: your call is being forwarded and the number you are trying to call does not exist. How do I solve it.

I don't know why mtn is saying not exist