Vodacom not taking off what I have paid.

I have been with vodacom for more than 20 years and have had no issues at all. Recently however I have struggled with them and taking off payments I have made. They phone and send messages on a daily bases saying I am in arrears. I have been to the tablebay mall vodacom shop 5 times now to sort and the issue with still no luck. I have emailed my bank statement to them with proof of payment myself and the vodacom shop also sent in. We have lodged complaint after complaint and the issue still continues. I have never and will never owe anyone cause I pay my bills asap. And this is driving me insane that the issue connote be resolved. I almost want to cancel my whole contract and move to another service provider they are harassing me so much. Please can you help me??????