Wireless CDMA question

[ManyBeers]

I'm not sure if this is the correct forum for this post but here goes anyways...I currently use" Earthlink Wireless Enhanced Access ",for my internet connection. This service uses the Sierra AirCard 555 CDMA adapter. I basically can get Internet access anywhere a cellphone would work,however it is a bit pricey at 79.95 a month for unlimited data transfer. When signal is excellent it operates at about 120 kbps. To me it is noticeably faster than a 56k modem, however I heard it is possible to use a cellphone and plug it into a usb port(or whatever) and the pnone will do the same job as my aircard and since i need to get a phone I was wondering if this is a viable alternative and if the performance would be equivalent to my current setup both in data speeds and costs?