Handed over for account that's already paid!!!

Absolutely pathetic service! I have a Woolworths credit card, installments have always been paid online. January I paid my installment as per usual however they start calling me from Feb every second day, sending me sms, emails to say I haven't paid. I went in store Canal walk, Cape Town spoke to the manager, gave her my statements yet again but still they haven't rectified the problem, they just keep calling me for money!!! Absolutely ridiculous when I pay my account every single month without fail. They have now handed me over to attorneys to collect money