Bad Business

I cancelled my 2 year contract a month ago , it was due for cancellation anyways , I was told 13 March would be the last day and that I would be liable for payment until then .However, the internet stopped working on 28 February, I called the service Centre to report this and was told that I would be liable for call out fees if the fault is on my side when a technician is dispatched (+-R350.00). I refused this; how can I trust this? Yesterday I received a bill from Telkom for the entire amount for March, which I think is unfair, I was prepared to pay until the 13th not 31st, even though the internet has not been working since 28 February. Really unfair guys. I will not be doing business with Telkom again.