I would recommend skipping the Mogul and going straight to a Touch Pro, if you can.. The retail price difference between the 2 are only $30 dollars... $579.99 for the Touch Pro and $549.99 for the Mogul... The performance of the Touch Pro is a lot better then the Mogul.. Ask if you can sign a new contract extension, and pay $299.99, since that is the price a Touch Pro goes for with a new 2 year contract..
If anything, stay polite and be reasonable.. They are in the business to make money after all so if it doesn't work, be nice about it... Here is a thread about people being able to get Sprint to upgrade their Mogul's to a Touch Pro.. I know that is not the situation you are in, but you might be able to gather some advice from it..
http://forum.ppcgeeks.com/showthread.php?t=39341
Before you go to the Store, you might want to try emailing E-Care first... Mention something about switching to a competitor if your situation cannot be resolved... But be nice and you should be able to receive something for your time... At the worst, you might get a new 6700.. At best, a new Touch Pro for less then full retail.. I wish you the best of luck...