Unfair judgement against credit report.

A few months ago I cancelled my ADSL with Telkom by calling their contact centre. It took me a few attempts to get it cancelled and each time I spoke to an agent they did not inform me of any additional charges. 2 months later I received a call from Hammond Pole Attorneys saying my account was handed over to them. I settled the account immediately. My issue now is that Telkom placed a judgement against my name and I only found out now that I need to apply for a homeloan which was declined because of this. I received no letter from the Sherrif of the court to inform me that Telkom will be actioning this. I cannot provide a roof for my family because of the R350 that my credit report show that I owed Telkom. Now I have to pay thousands of rand to clear this judgement all because the call center agents did not inform me of a silly R350 or any cancellation fee. What do I do now in this regard?