Edgars just takes money that they owe you!

I had a balance of R29-60 in credit for many months. All of a sudden this was deleted with an entry called account credit adjustment. I made a purchase of R199-99 when I picked this up. Please give me my money back and rectify my account. If you ***** R30 from each of your clients can you imagine. Why on earth was this done anyway? I have tied to resolve this via mail - but yes of course no response!