[Triggaaar]

My wife is on O2, using Samsung E720

O2 have just called, offering a good deal - £15 a month for 12 months - first 6 months, 600 mins anytime, any network, last 6 months, 100 mins anytime, any network - and plenty of texts included too.

This would save her money.

She would also get a phone, but the phone would be limited to:
Sony E K608i, or LG U880, or LG 8380

She would just keep her Samsung, and we'd sell the new phone. The new phone would be limited to O2 and 3G networks.

Questions:
Is there a reason not to take this offer (they're calling back in a little over an hour)?
Which phone should we go for, and how much could we sell it for?

Thanks