MTN | Dreadful service and *****

I upgraded in early October, received the wrong device and then cancelled the upgrade. I have been debited 3 months of the new contract and despite regular call, messages to Mondo and MTN and in store queries, MTN continues to not sort this matter out. I am now in a 3 year contract with an old phone. I am at my wits end and have contacted ICASA to no avail