Call up angry and animated about how they put you on hold for fifteen minutes and never called you back and all you are trying to do is be an honest customer but now it is costing you do much time and inconvenience etc... Chances are they will apologize and tell you to keep it. If they start suggesting that you send it back, immediately get mad that on top of everything now you want me to go through the trouble of shopping it back to you?!! Get the idea?
This way your conscience will be satisfied;)