Nimble harassment

My sister has been to the edgars store in December 2020 and paid her account in full and closed the account. She even went back in January and again in March and the cashiers advised that the account is closed and that they actually owe her R38. However this nimble collection service sends her emails and sms's and calls her saying that she ows edcon R464 i then trien to assist my sister from calling on from my phone and speaking to the agent who advised tge same thing send proof of payment ect ect and now they are sending me messages about this account. They need to communicate with edcon and stop harassing people that are not owing them any money. If this continues we will be filling a case of harassment with SAPS as we have told them firstly the account number they have is wrong and secondly my sister has been to edgars and they advise tgere is no outstanding amount and that the account is closed