blocking Sim Card Porting

Having just said I was going to change my service provider from MTN, I stood for an hour watching the other company trying to get the code from MTN to port my number from my MTN Sim Card. Not only does MTN not provide a service, they are making it difficult if not impossible to move to some other provider and keep your number. They must realize that there is a flood of disappointed customers trying to get away, but obviously not doing anything about it