Useless accounts and just want to bully people into paying over money

Absolutely useless. Three months after my contract ended with another gym, the Gym Co took over. A year later they suddenly started calling me saying I owed them money. Yet my contract with the previous gym had ended 3 months prior to them taking over, and I've given them details on my contract which was for a fixed term anyway. Also why start calling a year later? Now they keep claiming they never received my mails and the proof of cancellation. They are absolutely useless.