Expedia Expedia.com Best Price Guarantee Refused After taking the money In spite of a promise to adjust the price, Internet

I booked a cruise on Expedia.com and within hours I found out that their own website was offering much better price for same date and same cruise for $150 less than what I paid. Their website says "We're so confident youll find the best price for your trip here on Expedia that we guarantee it. Find a cheaper trip within 24 hours of booking and we'll refund the difference-and give you a travel coupon worth $50." I showed that the customer service rep on the phone and also showed him the price. He admitted the price difference and said he is going to give me a credit. He said he is going to call me back the next day. He never called back. When I called him back after a few days, he said he remembers me and will do something about it and asked me to call him back later. I called the next again and he asked me go ahead with cruise and call him back after coming back. 

I promptly called him after coming back from cruise. He acknowledged our conversation and said he is going to process the credit immediately and said I should get an e-mail within 2 business days. I never got the e-mail back. After that I could not reach him. When I called after a few weeks, someone else said he left the company. She said she could not verify our conversations since their systems changed. She said will put in a request to check the old system to check telephone recordings. 

Two days later one other lady called and said they do not hold voice records and she can do nothing about it. This is totally ridiculous and they wasted my time hours and hours on phone with different people and finally refused to do anything. The lady was so rude on the phone she says she can not honor a promise her employees did since they may have mislead me. I am not sure where to go and how to resolve this. 

Please help.