Appalling service received with query

I contacted Telkom Mobile for the first time on 2 October 2015 regarding my account. My contract expired in August 2015, in September 2015 I was billed on a month to month basis for the data only, the billing was R99. In the beginning of October I received a billing for the same amount of data, however now the data was almost R600. I contacted the call centre to query the new billing amount. <br> The first agent said he could not assist as he did not have access to that specific billing. The second agent said there was a billing error and I will only be charged R99, a third agent called me almost a week later to say that the billing is correct, they are allowed to just charge me the new amount since I am no longer going to get the discounted rate. He then said he would only credit my account if I go and upgrade my contract and that I should send him an email once done, then he will credit the amount. I went and upgraded the contract and have sent the agent numerous emails, yet he never bothers to respond. I called the call centre yesterday again. Still no feedback received. - The service has been appalling to say the least.