Supersonics pathetic service

Supersonic has still not refunded me for a mistake they made, I have been calling them for the past 3 weeks whenever someone did answer all I got was that the billing departments manager needs to sign off the refund, this cannot take so long to do I was also told I will get refunded between 7 to 21 days which has passed already, I tried to call them today was on the line for 15min no answer, at this point I'm really frustrated seems as if they will only sort out the problem once you at their offices face to face then they won't be able to give the same bs excuse that they give over the phones!!!