If you’ve got an iPad and you occasionally use the $15 a month cellular data plan option, there is a way you can save a lot of money (and get more data!). The $15 data plan gives you 250MB of data per month, if you go over it either runs out or you have to start the next month early. 
AT&T has a new $25 plan that last three months and gives you 1GB (1000MB) of data. That works out to 333MB a month for about $8.33 a month, about a third more data for close to half the price. The other benefit of it is that since it’s spread over three months you could use 600MB one month, 100MB another month and 300MB the other month. It gives you a better chance to utilize more of the data since it doesn’t expire three times after 30 days, it’s once after 90. It also doesn’t auto renew, so after 90 days you need to add that service again; the benefit to you is that after it expires if you don’t use it for a few weeks, those days don’t count against your next 90 day block. This is in the United States, I’m not sure if they’ve adjust prices in any international markets yet.
I think AT&T is doing this to get people to use it more, some people would turn it on for a month and then turn if off for a month, this way they spend $25 instead of $15 and if they don’t use it AT&T makes more and if they do use it more, they might get hooked.
At this point it makes almost no sense to turn the monthly $15 plan on and off a half dozen months throughout the year (that’s $90), for $10 more you could have it on every month of the year and have even more data to use. If you kept the new plan for the whole year it would be $100 for 4GB of data, the old plan would have been $180 for 3GB of dat a (with monthly expiration).
This is now cheaper than the cheaper data plans on the iPhone. Right now you pay $20 a month for 300MB of data (some people still have the $15 for 200MB data plan), that’s $60 for 900MB of data. That’s quite a bit of difference!
FYI, if you almost never use the cellular data, but once in a while wish you had it, they also offer a new plan for $5 for one day that gets you 250MB. This is not meant for daily use, but if you’re traveling for the day on train or waiting at airports, it might be worth it. Or even if you activated the data plan once in a while while you were traveling for the weekend, doing the $5 plan could be cheaper for two days ($10 instead of $15) or actually get you more data during that time.
just released the 4th book in her excellent Saving Mars series (titled 
