dishonest and terrible service from accounts department.

I took my son for his annual eye test at the Hillcrest branch and he was prescribed glasses. We did the usual.. had a look around chose frames that suited his face and requested a quotation. The quotation was sent to medical aid and I was asked to sign the quotation showing that medical aid would pay the total amount and due by patient was zero. I signed it off and asked them go ahead. They had his glasses made up we collected them. Then 3 months later I get an email with overdue account. Shortfall on Medical aid and I was asked to pay in R 1639.36. I of course argued this as I would not have given them the go-ahead if the medical aid had rejected it or said there was a spend limit of some sort. I would have asked my son to choose within the medical aids budget. I feel I have been bul**** with threats of blacklisting to pay this account. I have paid it although I feel it has been a completely ********* way of doing business. Why have a quoting system if it stands for nothing.