Non responsive customer feedback

Have been collecting my grandmother's chronic medication from Dischem Ballito Junction for years. Not the friendliest pharmacists, which is fine as I collect from here out of convenience. Medication is never dispatched without surcharges being paid on collection, which has always been the case and we are happy to pay on pick up.

Received a statement IN November 2019 for an amount of R260, 00 stating over 90days in arrears. However no invoices or details of what this was for. R260 is nothing in comparison to the large amounts spent on meds, however, one can't pay blindly as we have never had an "account" with dischem. No further correspondence was since received and nothing was mentioned when we visited paid and collected meds since. We however receive a "final demand" letter and statement once again yesterday. I responded to the email once again requesting details and a statement and investigation as to how and where did this amount come from. Still no feedback or response. The email was from a Margaret Gomes.