To use your cell phone as a modem, you need the following:
1. The device you want to be able to go online with (i.e., your laptop or PDA)
2. A data-capable cell phone (i.e., the cell phone should be able to go online on its own).
3. A data plan for the phone from your wireless provider. Most cellular providers these days require you to have a data plan for your smartphone anyway, but regular (or feature) phones may also be web-capable and therefore can also act as modems for your laptop. You'll need to have a data plan for the phone, whether it's a cell phone or smartphone.
4. Either no restrictions in your contract for using your phone as a modem, or a separate, additional data plan that allows tethering
Tethering Instructions by Wireless Carrier
Find your provider below to get information on whether they allow tethering and how much it costs. If you're in the market for new cell phone service, read through all the profiles to find out which cell phone company is the most flexible when it comes to tethering