Very bad service and locking our property

We have an Iphone 4, which was on a MTN contract 2 years ago. We gave it to my mother, and she now can't use the phone, because MTN network locked the phone. It is our property and they have no right to have locked the phone. Now they want us to pay to unlock the phone, which we refuse as it is not MTN's property or right to lock it, and we now had to send it in to the technical department and they now tell me they haven't even received the phone. <br> <br> We want the phone unlocked without charges and we want it done quickly. We will cancel all our MTN contracts due to the very very poor service, waiting 2hours in queues to be helped and then not even being helped. We will also take this up with the consumer protection act as MTN is prohibiting us from using our own property.