Are you talking about the auto key lock? It might be stated somwhere in the settings, or in the manual. IDK, I'm not familiar witrh the W42S. However, user interface should be the same as with any other SE phone.
If you're looking for a
GSM phone to work on T-Mobile that's almost comparable to the W42S, you might want to consider the following:
W850i
W830i
W580i
S500i
W910i
For more info, check out the link.
Phone Finder results - GSMArena.com