check out straight talk....only $45/month.The thing that scares me is that MVNOs can fold over, overnight, and you would just lose your phone number. Look what happened to Amp'd Mobile, Helio, and the other MVNOs out there. The only MVNO that seems to have stuck around is Tracfone and Virgin Mobile.
Is Red Pocket Mobile stable, business wise?
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YouMail is not only on Cydia, but the Apple app store as well, see for yourself .
It is worth it for the "hangup" notification alone.
i'm not worried about it...i ported my number to google voice when i left AT&T. you could do the same if you are worried about it...google voice is awesome.