Can I use a Straight Talk GSM SIM card for laptop internet?

Hey guys. I had a question about using a GSM SIM card for laptop internet usage. There is a cell phone provider called Straight Talk that is created by Tracfone and is sponsered by Walmart. They offer an unlimited data plan for $45 per month that can run on the GSM network which typically uses SIM cards that are usually removable from the phone itself.

I was wondering if I could order one of these GSM straight talk phones on the unlimited plan, take out the GSM SIM card from the phone, and put it into my air time card reader and have it work to access the internet on my laptop. I have read stories of people having success doing this with another cell phone service provider called T-Mobile.

The exact airtime card reader I am using is a USB device called a 'Model 4597 3G+ Freedom Modem for AT&T and T-Mobile' that is made by a company called Zoom Telephonics. It claims to work on AT&T and T-Mobile GSM services, and it also says "and other GSM cellular data services worldwide". A link to the product page would be here:

http://www.zoomtel.com/products/mobile_broadband_overview.html?gclid=CLX0nKCq2KcCFZFoKgodciSg_A#4597

Will this idea of mine work? Have other people been doing this? The reason I am asking is because when I talk directly to AT&T or verizon they want alot more money per month and they also want me to sign a contract which I don't want. That's the great part about Tracfone Straight Talk - it's the cheapest unlimited plan I've been able to find and it also doesn't require a contract.

Also, it sounds like Tracfone Straight Talk has a soft cap of 5 gigabytes on thier unlimited plan. I guess if a user goes over 5 gigabytes in a month's time, they risk getting thier account shut down, right?