Unexceptable service

I had a contract on my sisters name for myself as I did not have a credit score. So when I eventually got a credit score I was able to change the contract account to my name. So I went to Vodacom 4U Walker Drive (worst mistake)to go and change the ownership of the contact to my name. The sales consultant or must I call him unexperienced consultant David to help me as he went to jump up and help me when we got there. We were struggling for about 2 weeks to get the contract transfered and when it got transferd it was done wrong. As we expected it wouldve been wrong. As he wasnt really helpfull. My contract is suppose to be a R300 odd amount but now my debit order whent off a total of R676.00 which is not unfair as that was not the arrangement. I have this contract since Feb 2019 and this is the first time I have problems with Vodacom as I used to work for them back in time. We dont have money to waste at this time. I feel like David needs to go back on training or I will personally give him training myself. Please see what you guys can do for me as this is not the first time I was charge the R676.00 Thank you.