Unable to afford membership

I only went to the gym once. I find myself unable to afford my gym membership as I didn't get an increase on my salary and I end up with no money after paying my debts. I have tried to cancel it, they want to charge me R2000, I asked if I can pay it off, they said no.

I tried to freeze the account so I can pay my debt, they say that I will pay R125 p/month plus my levy (which is R400)

I'm hopeless now. I can't pay them and they don't want to understand my situation as they are a big company that doesn't care.

What can I do now? Even if they blacklist me and send someone for collections, I don't own anything other than my clothes and a very old acoustic guitar.