My mtn line is not receiving calls, sending or receiving sms. What could have been the problem?

I have not been receiving sms,calls or airtime subscription from my mtn line of recent since I relocated to abroad

The message I keep getting when i try to call my Mtn line is that I can’t receive calls at the moment

My mtn line no longer receive calls nor I can call +256787027919

I used to be able to send and receive both SMS and calls from the US from my MTN. But recently, I can no longer do any of that. I do recharge my phone periodically to keep...