2001 draining battery

A couple of months ago, the word "CALL" started to show up intermittently on our radio display. Looking in the Ford manual, it says that this display is related to the WIM (wireless interface module). Our car does not have the center console hook-up, but our radio seems to think it does. After finding a dead battery one morning, we took the car into the dealer who thought the problem was the radio so he changed the part in the dash board. That was replaced with a new radio, but the next day the "CALL" still showed up on the display. The dealer reinstalled my original radio. Then I called another dealer and he recommended I remove the amp/tuner in the trunk, which we did. The battery is still being drained as we went out 2 days ago to find our new battery dead. We had the battery recharged and a day later, it's dead again. I've spoken to 4 different Ford dealers and no one has heard of this problem before. One mechanic thought the problem could be related to water in a module, but they haven't found any. One of the dealers was kind enough to call the radio manufacturer, but they hadn't heard of this happening either. Any ideas/suggestions?

Thanks