For those times when MWI is stuck on:

Find the MWI off DN.

ephone-dn  599
 number A801…. no-reg primary
 mwi off

Build a new DN which has CFA set to the complete dialstring (fill in the …. with the extension you want to turn MWI off on). The below example will shut off MWI for extension 5040.

ephone-dn  559
call-forward all A8015040
number 5990 no-reg primary

Call the number associated with the ephone-dn.