Problem not getting sorted out

In 2011 I got a personal loan for the amount of R15000 through Capitec in Meyerton a few months later I decided to consolidate all my debt through standard bank. Capitec was one of the accounts that was paid in full in 2011. I never heard from thenm again. In 2014 I got a call from a debt collector with the surname Booysen he said that his calling regarding my Capitec account that is outstanding I said I don't have a account anymore it was paid up in 2011. ll proof has been sent not once but many times Capitec sends me to standard bank and standard bank send me back to Capitec and I get called all the time but yet proof has been sent that it was paid in full. I don't know anymore what way to go I'm loosing time at my job and can't afford taking time off anymore just to end up at a closed door. I'm really disgusted with the service.