Pathetic service

So my account is overpaid with R500 and I need a refund and Vodacom goes and lists my overpayment as a missed payment with the credit bureau. My score has dropped significantly and when I talk to Vodacom customer care they tell me they can see that I have a credit of R500 and it will be paid back. No one has called me in almost 2 months regarding this and they keep me listed on the credit bureau. Pathetic customer service!