Credit Limit Query

I previously raised a complain with cell Con Tuesday pertaining my credit limit- I basically made upgrade with Cell C on Saturday at Centurion mall and I signed paper work setting my CL on R100 and 3 days later I then received a call from Cell C advising me that I owe R1500 on my contract and the lady failed to explain how my bill got to that amount with a credit limit of a R100... To-date I have received 1 call from Derrick Makubele who informed me that they were doing investigation and will revert to me on Thursday but did not. I requested all the signed documents from a store manager Nathan 2 days ago and till now I haven't received them.... The lady who assisted me with an upgrade named-: Shaney informed me that my credit limit was amended 6 times from the time I signed up for the contract and there is no call recording that suggests that I might have called in to request a change to it.... This issue has given me an indication that customer satisfaction is non existent in Cell C... I am a customer service manager myself and I expected a better service from Cell C and staff... Seemingly there is no 1 competent to deal with issue promptly.. disappointed and regret why upgraded!