Most carriers do have a text limit per month. Usually around 300 send/receive...once you go over, it costs you like 5 or 10 cents per text received or cent.

Most people just never go over the limit so they never realized there's even one.

Got a prepaid for Michelle recently (just tired of worrying about contract and just need something simple) with Virgin Mobile and they have a package for 1,000 send/receive texts for $10. With the packages we have, the monthly cost is the same from when she had t-mobile. Virgin easily has the best pre-paid plans since it's nationwide long distance as it uses Sprint's network and has pretty much the same rules. In the bay area, have had the most success with Spring so glad they use that network.