Disgusting service

I have been a customer for MTN for years, I have been using the number to receive smss , I have also registered my banking app to receive smss, I have registered the number, I have the sim inside my phone for all these obviously. Now theh have gone and deactivated my number???!! How??!! Why??!! Where??!! What for??!!! I'm trying to authenticate a banking transaction I cannot I am stranded because of them. I never received a phonecards or anything to ask me if I still need the number, which I'm obviously using. This is ridiculous. I want my number reinstated immediately