Gym Company is a ****!!!

A ****!!! I received a WhatsApp a week ago saying I owe gym company R1000 or I should pay R500 to renew the contract and cancel the old one. I haven’t had a contract with gym company since 2014 and don’t owe them anything. This is the second time that I’m receiving a WhatsApp and when I contact them they don’t respond to my query!!! Very frustrating. They are claiming money I don’t owe them with non existent reference numbers that don’t match the membership number I was using when I was part of their gym. SIES!!!!!!!