Yes, they could not do anything. If you look elsewhere in this community, this is clearly a problem phone that was messed up even more by the ICS upgrade. You can see that plenty of other people are having the same issues as me with this phone. Anyway I've just signed up for my corporate phone service, I am porting my Sprint number to Verizon after 17 years as a Sprint customer, because I can't afford to pay full price for a decent phone and I can't wait another year to get a new one. I was also not impressed that after spending all this time discussing my 4G issue in this forum and on the phone with Sprint, nobody except for me thought that it might have been an issue with the phone (rather than a reception issue) and I was the one that solved the problem by doing a very time consuming and disruptive factory reset (time consuming because of the amount of reconfig that needs to be done afterwards).
I am sorry to hear that you are leaving Sprint. I have notified our product management team in regards to the issues with the HTC EVO Design after the ICS update. Hopefully we can get some sort of maintenance release update to resolve the problems.