MTN PAYBACK MY MONEY!!!

MTN billed me for months for a device I never received, after months of contacting MTN customer service and nearest branch, retentions department finally when I asked for the figure that was debited in my account for months and only then MTN CHANNEL QUERIES responded to the cancellation and this was in June but still no refund until today. The sad part is that if I was the one owing I could have been blacklisted long time ago, I need my refund please!!!