Mtn disconnected simcard

I Have been using Mtn simcard for more than 3 years. 6 months ago I have changed my simcard to contract. Recently it has stopped working "it not reading when I am inserting it. I call Mtn customer service they gave me reference number to make follow up, i did make.follow up they saying it's disconnected from server there is nothing they can do I should wait until it's connect Mtn offices they saying the same.thing. I am defeated because the interview, courier, debt collectors can't get hold of me.worse I can't do si swap. So disappointed in MTN because I ask them what the reason of disconnected no one is sure it's always a different story.