Harrassed over settled account

I have been in a struggle where planet fitness has been inappropriately billing me. i had paid upfront for planetfitness special, which they later converted into a contract. after my promotionally period had expired they claimed i owed them money. that went on for months until i finally paid and asked them to close my account both the lady they were using at saya recoveries which i assume is their debt collectors and the branch which was in tygervalley. Four years later, they come back claiming i owe them R10 000 rand , to my shock, i have never used their services and 4 years later a contract creeps up. i told them i will not pay and i will report them to consumer protection. i mean how pathetic and greedy can a company get? they keep harrasing me with emails that i owe and for months then they disappear..they dont even have an email account where you can place your complaint on record, except through telephones.