woolworths claiming that i still owe them

woolworths lawyers( Norman Bissett Associates) is claiming that i am still owing them a credit card that i settled last year December 2014, they have been phoning me stating that i have a loan and a credit card with them off which i never apply for any loan from woolworths the only thing i know is the credit card, i then get an offer to settle my acc with them i then did settle the account only to find out they settled the loan that i have been telling them that i never app**** for a loan with them now they keep on phoning me asking to pay the credit card that i know that it was settled