Contract dispute

I had signed up for a 1 year contract with my father in in 2017. A year later I renewed my contract for another year with my girlfriend. They never gave me a hard copy as they would send me one digitally, although my girlfriend "A first time member" received a hard copy. A year later we tried to cancel our contracts as we are moving. They said it was a cancellation fee of around R6000. I queried it, and it turns out that a guy in Joburg who handled my contract digitally forged my signature and wrote down 36 months instead of 12. Luckily my girlfriend has her hard copy and proved it was 12 months, but unfortunately for me. I don't have my hard copy, as I never received one. The manager of the Musgrave branch said there isn't anything he can do, and I must pay a cancellation fee of R3700. As you can imagine, there is no way I'm going to be paying for something that's as forged under my name. To this day, I've been blacklisted by them, and to try get ahold of the manager or the accounts department for around 2 years to resolve this issue, has been a joke. Legal action will be taken