Overcharged account

Hi MTN,

I have a complaint, my account has been over charged for a device that I have returned to your stores within the 10 working days of me receiving it. I have called the warehouse and they have confirmed that they did receive the device and gave me a reference number. However, my account still reflects an amount that I don't believe I owe. I have been calling your customer service support for close to a year now since this happened at the end of August 202, however no one has resolved the case. I am not happy with your service and I would like a resolution to this.