Bad credit score due to very poor/delayed service

I app**** for Telkom mobile contract July 2015 and later requested cancellation as I was no longer interested. The Phone was delivered, no contact person/details in the case that you want to make an enquiry or you are not satisfied. I called 10213 and put through thousand agents who could not assist until I got cut off. Kept on calling with no success. I eventually went to one of their branches at The Glen Mall to take back the phone and I was told that they don't deal with online applications. I finally got Siyabonga Msane one of the representative and I had to fill in cancellation forms and send them my address to come get the phone. I did all that he promised to process the documents and send someone to come get the phone. I wanted months and then made another call seeing that no one is coming to get the phone and I was receiving statements, I was told this will be sorted out. I sent numerous e-mails to Siyabonga to assist but nothing. Today I have a bad credit record because I now owe Telkom for a contact I cancelled 5 months ago. This was a shock as I did all they told me to do but nothing was done, now they handed me over to dept collector for this??