Refund never received

I cancelled my service and sent in the equipment.  Was charged the equipment non return fee - two weeks later Directv finally receives the equipment but I never get my money back!  I've chatted with support once and no credit received.  Spoke to some sort of escalation Department and STILL NO CREDIT.  Eavh time I am promised that I will get my money back but to no avail.  Who can I call to get my $151.88 back? Help!