Telkom ballito duplicated my contract and I'm now paying her twice every month for the same thing

I took a contract from Telkom in ballito(initially lifestyle centre) for data and a modem in feb 2017. At the onset the service didn't work I took it back to the shop and after a few visits they finally sorted the problem out by issuing a different SIM card. I later found out that they had duplicated the contract and I have now been paying twice every month for the same contract since February 2017. I've sent many emails to the staff member responsible. Only to receive replies saying she will escalate the complaint however nothing has been done and she has since stopped responding.