Why can't i receive or make calls with my Nigerian Mtn sim card here in the UK?

I can't make calls and recharge my line

I can't make calls with my MTN line but I can receive calls and sms. What can I do to be making calls with it

My SIM card is not working again. I can not make calls, receive or send messages

Why can't i receive or make calls with my Nigerian Mtn sim card here in the UAE? I have tried to reconnect my MTN Nigeria and is not coming up. I also enter the number in MTN...