Wrong billing

I recently upgraded my phone and I declined their insurance. When their debit order comes through it comes through with their insurance which I declined. I've complained about the matter when the first debit order came through, was notified that the matter would be corrected and I'd be refunded the following month and the insurance will be cancelled. I have never received great service from MTN. and as of today 20_01_2018, another debit order came through with the insurance. I am sick and tired of MTN. I would like for them to cancel my contract with them as I have been mistreated and billed for something I don't want. And I would like my money back... I know it's not a lot, but it's money which wasn't supposed to be taken from. I would be more than happy to return the phone. Can someone with higher authority please contact me so that I can return the phone and in turn get my money back