The bottom two lines will always appear. Third line up from the bottom can be changed on the BCT15 & BCD996T (mode 1 / mode 2) displays. There is no way to just turn these lines on or off. Another display option is Active Channel display.
To change from mode 1 or mode 2 on the BCT15 & BCD996T press HOLD - FUNC - 0 . this only changes the info on the third line up from the bottom. If you are seeing the freq on the second line down from the top, you can change that in the menu by using edit name in the menu system.