Plane Fitness wants payment two years after cancellation!

I was on a month-to-month basis after completing my two year contract at PF Parklands, long story short, I moved so I gave the required 1 x months notice and paid up what was due (or so I thought), Now, over two years later, out of the blue I get an email from Saya recoveries informing me I still owe R617-08! For what? All sorts of threats if I don`t pay up! I think this is just a fishing expedition hoping I will take fright and cough up! Sorry, not happening - ever! With all the complaints I am actually surprised PF is actually still in business. Pathetic!