Expedia / cancellation of flight/refund

We booked flights for Christmas from Anchorage to Acapulco in June, 2008. The credit card was charged about $5, 100.00. On August 14, 2008 they called and said that the flight was cancelled. They said we would get a refund "within 3 billing cycles." On October 24, 2008, I called the airlines (Delta)directly about this. I was informed that Expedia never requested the refund for us, even though we were entitled to it. Now we will get our money back in 7 to 10 days (hopefully). Bottom line is that they sat on $5, 100.00 for 5 months.