RE: CELL PHONE INTERNET ACCESS
For AT&T the data plan for tethered phones is Data Connect. The $60 plan is 5GB. The feature can be turned off and on but I don't know about prorating. You don't need their software. Just create a dial up connection to the phone via bluetooth or USB cable.
AT&T data plans for plane phones. Not for PDAs or smartphones. The have another for them.
Wikibooks - AT&T Mobility FAQ/MEdia Net Configuration - how to
AT&T appears to tolerate, or at least not to monitor actively, tethering of phones that have the Web access feature installed. The feature was called MEdia Net, and is now called just Data Plan. It costs $15. per month, or when combined with 200 text messages per month, $20. per month. As noted, you use it by creating a dial-up connection. I have two phones with this capability, one of which used it almost daily for several months with no problem. AT&T's 3G service is pretty limited, but where it is available, the tethered connection operates at 3G speed.
RE: CELL PHONE INTERNET ACCESS
Casey and others may chime in that they have no such limitation on their EXISTING contract, but that may only be true because the limitations came into existence after the start of their contract date.
Just for the record, I don't know whether or not there is a usage limitation in my existing contract. Further, I don't know whether or not ATT is content to allow tethering, perhaps at some level, under their Unlimited Media Net service, or simply hasn't recognized that I do it. I do accept, cynically, that "unlimited" does not necessarily mean unlimited.
RE: CELL PHONE INTERNET ACCESS
I have two phones on an ATT Family Plan, a Motorola V3xx and an LG Shine. Each of them has a $20/month subscription for "Media Max 200 Bundle", which consists of unlimited Internet Media Net service plus 200 text messages per month. Both phones are tethered to their respective PC's. One was used as its PC's only Internet access for several months until recently. The other is used as a periodic backup to a sometimes unreliable ISP connection, and for access when traveling.
The maximum usage of either of these hasn't exceeded 2 gigs in a month, so I can't know whether ATT would catch them at 5 gigs, but they surely haven't caught either one in over a year of moderate usage. It's fairly clear that the Media Net service is only intended for use with the phone's internal browser, but ATT's web site still carries an old Cingular instruction sheet for setting up the tether connection. Where 3G service is available, the connection appears to operate at 3G speed.
