I don't think UA is trying to cheat you. I think their software is greatly fouled up. Before TED was euthanized, I booked C class award travel to Europe from LAS. The domestic connecting flights into and out of LAS (from IAD and LAX) were on TED and since my status had expired I went on line and paid extra for E+. (Yes, illogically, you get E- on C award travel if domestic F is not available for some leg of the flight.) Then, before my trip, TED was killed off and I got domestic F in and out of LAS. I called and asked for a refund of my E+ payments. UA agreed but the credit was less than it should have been. I called again and this time the additional credit was more than it should have been. The incompetence works both for and against UA.