Migration From Contract to Prepaid

I am writing today to complain about the terrible service I've been receiving since Saturday 06/06/2020. I have 3 contract numbers with MTN. One number was migrated from a contract to a prepaid on Friday 05/05/2020. Since the migration I can't receive any incoming calls. I've been calling the call centre and no one can resolve my issue. I need this rosolve because it's my Primary contact number