Mtn worst service ever

I have been trying to cancel a contract from Mtn since April. They sent me an incorrect device. Sent the devicd back to them and they promised to cancel the contract. Up until today its not canceled. Everytime I call them they promise it will be canceled. Now they are telling me about cancelation fees. How do I pay for a device that I dont even have??? 😡😡😡😠😠😠