Wonga refuses to pay me Refund

I took a loan from From Wonga on 30 January 2015, on the 18 February 2015, I paid it up. On the 27 February 2015 they went and deduct money again from my bank account. <br> <br> Same day I called them for the refund, I was told to I'll get my money back in 3 working days, Even today (13 March 2015) I haven't receive my money back. When I call them they tell me they have trouble with doing payment, but when you take a loan they pay immediately. <br> <br> Its been 15 days Wonga having my money and I don't receive even an interest on it