ZONE FITNESS - HORRIBLE AT ADMIN

I do not have an account with Zone fitness, have cancelled membership in 2018 or 2019. However have received a letter of demand today. I don't understand how this is possible as I have not used the gym or had any debits go through since I had cancelled about 4 YEARS AGO. In December of last year the debt collectors started harrassing me and left me alone once I clarified the situation and today I received an SMS stating to pay in order to avoid further action. This seems to be an ongoing issue as Zone Fitness cannot keep up with their admin or even know who their current clients are.