SMS service blocked for the fun of it 😡

Outgoing SMS not going through for 2months now. MTN keeps on telling me to update SMSC number and switch off my phone for some minutes Clearly call center agent have no idea how to resolve this simple problem. Matter was escalated to their "technicians" but no improvements after 27hrs. 1 call center agent says my sms service is blocked "sometimes Xtra time causes these problems" I never used Xtra time service.