If you don't like commitment, a prepaid phone plan can be appealing -- but not if you have to predict your data needs well in advance. Verizon may offer a lot more flexibility with its new Allset plans, though. While there's only one base $45 per month plan for smartphones with unlimited calling, unlimited messages and 500MB of data, customers can tack on "bridge data" that rolls any unused megabytes over to the next month. If you pay $10 for 1GB of data or $20 for 3GB, you can hold on to any leftover capacity for up to 90 days -- a big help if you know you'll need some headroom during that summer vacation. There's a $5 pack if you only need 500MB of data for 30 days, and basic feature phone users can buy the same bridge packs. Basic feature phone owners can also use Allset, although their $35 base rate caps them at 500 minutes of voice. These aren't the cheapest prepaid plans we've seen in the US (see Virgin Mobile for a good example), but they may make sense if your internet usage varies wildly from month to month.