Charged for a service I didnt request

Late February I had a line installed and got myself setup with ADSL through Afrihost.<br> My first bill arrived from Telkom which was R1170 odd rand which I paid as it was for the installation of my line etc.<br> <br> Then I received my second bill from Telkom for March and I assumed it would be R120 or whatever the amount is for line rental monthly. I expected this bill as Afrihost was unable to migrate my line due to some issue from Telkom side. But when I checked my invoice they were billing me for a total of R470. I phoned and raised a dispute about my bill and was told that they would credit my account once they have completed their investigation. But in the meantime I have to pay the R470 otherwise they would suspend my account. Whats more is if they determine that the billing was wrong on theyre side they would not pay my money back only credit it to my account for future expenses.<br> After spending a massive amount of time on the phone with their call centre still nothing has been resolved. I do not understand how my line rental can be R470 and they do not show any other details on my invoice for me to see if they are charging me for something else