MTN DISLOYAL

I have a data contract with MTN for R199 per month, this morning I got a notification that R320 was deducted from my account, when I called to cancel the contract, they can only pick up a R320 contract that I have no idea where it came from, I was delayed and made wait, the call took 24min, but still the contract was not canceled, the lady asked for my ID number for about 4times after making me hold to verify, she is still convincing me to take another contract, if contracts in their system just change on their own and take more than you agreed with them on why on earth would I have another contract with them? I asked if they were giving me my R120 back but there was no response to that, I have been such a loyal customer with no arrears, ai deserve better than this.