Fully paid customer but handed over

The below message from the lawyers, I was shocked that I'm handed over to the lawyers. I don't know how because the spectacles that I bought they are with me and using them. I don't know how did I receive my spectacles if I was owing

Someone did not do his or her job properly that who will be blacklisted. Is it what they do to all the customers. I will never ever set my foot again in any Specsavers. They are destroying my life.

Can Specsavers explain to me how did this happen

Dearr MS MTUNGWA

Please note that your personal information was processed by Van Rhyns Attorneys in order to inform you of your overdue account.

Your Outstanding account for Spec Savers Maponya Mall has been handed over to Van Rhyns Attorneys for collection. You are hereby given 20 days notice to settle the account inclusive of all legal fees on an Att and Own client scale directly at Van Rhyns. Failing settlement will result in a Credit Bureau Listing. Your Balance is R5962.44. Payment to be made to ABSA Acc no: ***. Ref 349865.

Van Rhyns Attorneys Tel ***.

Website address: http://www.vrattorneys.co