Telkom not able to manage accounts, they failed to help me.

I was once using a telkom ADSL and contract ended and after that they continued providing on a month to month basis and I was paying for that and then I decided to get LTE Wifi router, then I gave telkom a 1 month notice as they suggest and after that month they deducted the installment and made some charges I didn't understand and they closed their services. But a few months later they sent me some lawyers with a bill of R580 that I didn't understand where its coming from. And I explained to the lawyers all of that and asked to sort this out with telkom because I don't owe them and they went away and kept quiet since then. and today I losing a job offer because of that debt. And I don't know what to do because you call them for hours until your airtime is finished and if you managed to get them before they even give you the reasons for all that your airtime get finished and they will not call you back even though they have your number I lost hundreds of airtime try to get them. I need help with this issue and I don't know if I should sue the company for losing a job opportunity or what but I'm going to do something because even while I was still with them they made a lot of errors in my account that benefited them. in my last call I spoke to Hlengiwe Hlatshwayo and I was cut off by airtime that I bought for R150 because I was holding for a very long time, but still the lady didn't call me back even though we were not done.