Default on credit bereau

I never had a contract with gym company ,next thing they listed a default on my name on credit bereau for R540.00.I did not want to fight and argue over R540 and decided to pay the amount and sent the proof of payment to them its been over 4months now ,they still have not removed the default on my name.I have been calling and sending emails ,no response.This is not acceptable ,,,now I have to take further actions ,the annoying part is the fact that I never had any agreement with .I am really ****ed off