Pay-per-use cellphone plans are sometimes befuddling -- the rates can change depending on whether you're calling or texting, or how much cash you put on your account. T-Mobile thinks it can end this confusion with its new, much simpler Pay as You Go plan. As long as you plunk down at least $3 per month, it costs 10 cents for every text message or minute's worth of talk time; you won't have to guess how much credit you have left after a long call. It should be cheaper in some cases, too. Previously, you had to pay as much as 33 cents per minute for voice if you only bought small Pay as You Go refills.There are new data passes to go along with these basic options, although they're really meant for travelers and others who only need short-term access. Paying $5 per day will get you 500MB of full-speed data, while $10 will give you 1GB to use over the course of a week. You're still better off with regular service plans if you use your phone often, but the new offering could make life a lot simpler if you only occasionally need to get in touch with others.