In my opinion, RETURN THAT THING while you still can!
I did extensive experiments with a pair of LG420g phones awhile back, and both were pieces of crap, to be honest. Several intermittent types of malfunction, turning themselves off unexpectedly, rejecting their SIMs unexpectedly for no reason, unreliable operation in general, weird Asian pictograph-language error messages occasionally, somewhat crappy signal-grabbing, intermittently ignoring incoming calls without ringing or giving ANY indication a call was coming in (it dropped to VM for the caller), occasional unexplained continuous (many minutes long!) battery-draining high-intensity RF chatter while idle in standby mode for absolutely no apparent reason... etc. etc. If you want the gory details, search my prior posts about it.
Just a piece of crap all around. And since I tested TWO of them, it was NOT just a "bad unit", it was inherent to the DESIGN itself.
I got rid of 'em both and got a Moto W376G, which has been fantastic in all respects so far, especially 100% reliability (excluding AT&T tower problems beyond the phone's control), astounding signal-grabbing and excellent voice quality. I can recommend this model provided you want a TELEPHONE and not a music player, movie player, high-res camera, a handheld computer, or other fluffy non-telephone features on your phone. The W376G is likely the best GSM phone ever made in terms of grabbing a signal and giving clear sound, which is what a TELEPHONE is supposed to do well.
I'd advise you to ditch the 420 and get something else. It's just not worth bothering with, IMO.