Disappointed customer

I went to Jet Soshanguve Crossing to exchange 3 pairs of shoes which were about R310 total...I couldn't find anything else to exchange with so I opted for the money to be refunded back to my account. On the 16th I went to Jet Wonderpark and tried buying items totalling R290. I was then told my buying power is finished and purchase declined. What happened to the R310 refunded ????