Sorbet Voucher monies deducted when no services was rendered.

I am a very unhappy customer, I received a mothers day voucher from my children to the value of R 2 500.00. I had my first treatment at Castel Gate Sorbet. When I left the credit on my card was R 2 050.00. Two weeks later went for a fill up at Menlyn Sorbet, when I wanted to pay with my voucher card I was told that their system was not working and I could leave my voucher details with them and they would deduct the R 390.00 for services rendered, I received no slip so the lady wrote on the back of my old sorbet slip that the balance on my card should be R 1 615.00 after R 435.00 was deducted for the filler. Yesterday I went to Brooklyn Sorbet for a new set of Tip and Gel and when I used my voucher I was told there was only R 900.00 left on my card. I would like to know where the R 715.00 has disappeared to or has Menlyn Sorbert charged for services for other clients as I most certainly have not used it. I also wrote on the Sorbet website complaints for a response requesting a print out of services used on the voucher card and have had not reply. I would like to think that it was a error on the part of Menlyn Sorber and I would like to know whether the money lost on my card will be refunded to me as this is very disappointing. Tonia