Bad business practice - out of the blue arrears

Out if the blue arrear amount I was just told I owe gym areas 9 years letter just because I enquired about joining the gym again. I was a member of virgin active in 2011. 2014 I cancelled my membership. Since then till today I was not notified about the arrear amount or even been listed for debt collection. All of the sudden I am given a 50% discount. I am not even told what informs the 50% instead of 80/90 or even 100%.

I can't even prove that the arrear amount is legitimate as I don't have any 9 or 12 year records. I feel ******. If I never called or even requested to re-join what would have happened. I feel that virgin active is bullying me and treating me unfairly.