Frustrated by Woolworths

I had a woolworths credit card in 2014/2015 according to my knowledge i have paid this account in Full via a debit order in 2016. in February 2019 i then received an email from Lawrence Leeuw from Hammond pole attorneys telling me that despite of numerous attempt asking me to pay but i have ignored them of which i have not received any call or any notification regarding this matter and what puzzles me is that i was paying via a debit order when i ask what is this money for they never responded to my question and kept sending me emails that i need to pay this money. at first it was R600 and refused to give me a statement and said if i can pay immediately i can pay R400 now it has amounted to R 1127.08. this is really irritating and disturbing if i have had authorized a debit order how then i am still owing them.