Fails to refund money

I ordered a dog clipper from the supplier. order number #374, the end of January 2015. A couple of weeks later they phoned me to tell me that they did not have stock. I chose the option of waiting a little longer but nothing happened. Then I sent them another email on 25 March 2015 and they rep**** that they still do not have stock. They asked for my banking details so that they can refund my money. I gave them my banking detail and up to now nothing had been refunded even after I wrote them another email.