Lack of customer service

I am very disappointed with yellow sub trading.I returned an item that was on sale,they told me that they cannot refund me but they will give me store credit instead.I wanted to use that store credit to buy something,the number they gave me was not working.I contacted them and explained the problem.They promised to check with the finance department but till today nothing was done.I sent an email enquiring about the store credit but my email was ignored.