Cancelled account

I signed IP for a gym membership on November 2014 and was told it was going to be R99 p/m since it was an opening special and I signed a 6months contract and then a few days later I received a call they said the membership was no longer going to be R99 but a R100 and something rand then I told them I'm no longer interested because that was not what I signed for but then I never even went to the gym as it is I don't even know where the door is, 6 months later o discovered that they have taken my so called account to their debt collectors saying i owe R3800 for a membership I cancelled I called the gym no but thte was no answer called the nothe consultant was using it went to voicemail. Sent an email asking them to explain or clarify how this is possible and no one ever came back to me.I just want to understand how on earth I could be owing a gym that I never went to even worse for a membership I cancelled within 14 days and how does R99/ month go to R3800 in 6 months