Vodacom deducted my airtime and then informed me that I needed to repay an airtime advance

Vodacom deducted my airtime and then informed me that I needed to repay an airtime advance. This is very concerning because this number has been active for over 10 years and I have never taken any airtime advances. When I contacted customer care, they were unable to assist me. I also sent an email, but I have not received any response. Today, after purchasing a large data bundle, Vodacom deducted data worth R150 and again stated that it was for an airtime advance repayment. This situation is extremely worrying and I would appreciate urgent assistance.