Jet Debt Collection Harassment

I have a store account with Jet. I have had it for the last 4 years. I have been a good payer.

My payment methods have always been stop order payment. Jet then changed from Edgars to Foschini Group, and I never got any notification regarding this hence my stop order became null for the previous account they were using.

To my surprise I started receiving phone calls from Jet Debt counseling telling me that I have an amount overdue (an amount that is 3 times my monthly payments) which means they failed to collect money for 3 months due to the fact that I had a stop order with an account that is now not active.

I made yet another stop order with their now new account and am still getting harassed about no payments.

Its getting really frustrating getting calls as If I am a bad payer knowing fully well that I have never missed a payment.