Clears all MWIs, and gives the phone the test "Clear MWI" to discard.
==Known to work on
==Not working on
*Samsung Galaxy S2 (GT-I9100 - SMS received, but the MWU indicator does not show - tested exaclty the same curl to same sim in a Nokia E72 and it does work. Samsung ROM was 4.1.2, Cyanogenmod 23 October 2012
*Possibly HTC Snap