failing to provide service for two months

it has happened 2 times this year...i am on contract..lost my phone but mtn cannot do a sim swap...i am tired of going their shops..i have lost business clients and money..i wasted fuel going to their but they cant help ..the call centre very rude ..they say they cant help go to mtn store ...i have done 2 sim swaps but its not working on different phones ...its been two months ...without a service i am paying for ...this is the worst experience i have ever had