You can now put Three Pay As You Go sim cards into 2G phones and you will not get cut off by Three. It is as a result of their new roaming deal with Orange, which has given Three roaming charges cheap enough to allow customers to do this (unofficially). So if you use the bundle top up for £25 it gives you 500 minutes and £1.50 credit, although annoyingly it has an expiry of 30 days. You can buy pay as you go sim cards from Three for £10 or less off ebay.