Blacklisted for nohing

I went to go apply to get a car and found out i was blacklisted by Gym company. The worst thing is that i have never in my life joined a gym, when i went to go ask them about it they told me i need to pay them R900 to get me unblacklisted. I was approached by one of their agents years ago and he took my details and now suddenly without a membership card or ever entering their gym i owe them money. I refuse to pay for a service i never used, they rip people off, trick them into contracts and then blacklist you.