Contract contradicted 🚮

Asked them last year October to cancel my contract and agreed that I'll pay that cancelation fee over the period of 3months which Will bey monthly fee ,down the line they say I'm owing R6000+ meaning it hasn't been cancelled and has doubled up, then they send my account to some attorney named Saya debt collectors to pay that R6000.l told them I'll only pay the money we agreed on and nothing more and make sure they cancel my contract but nothing