I picked up a good deal on a Samsung Focus phone from eBay a few months ago. After TechEd 2011, I was interested in Windows Phone 7 (WP7) OS. At the time my office used AT&T for my company cell phone so I was able to pop the work SIM in and use it without getting an additional carrier plan.
Times change and I no longer have an AT&T SIM- and I really do not want to pay the crazy GoPhone data rates ($25 for 500MB!) or sign another contract and I started looking at alternatives.
T-Mobile has an prepaid 'unlimited’ talk, text and web plan for $50/month. The ‘unlimited’ allows for up to 100MB at 4G speed and everything else after that is 2G (EDGE) speed; for another $20 they offer unlimited 4G data as well. I was unable to find a way to use an old T-Mobile SIM I had on-hand so I purchased an inexpensive prepaid T-Mobile phone from Target ($20 for a Nokia 1661), activated it and promptly pulled the SIM an stuck it into the Samsung Focus.
The Samsung Focus is a quad band 850/900/1800/1900Mhz device and T-Mobile uses 1700/2100Mhz for its 3G network- so there is no possibility of getting 3G/4G data on this phone with T-Mobile; the $50 plan will provide unlimited voice, text & 2G data.
The Focus is SIM locked to AT&T- so installing the T-Mobile SIM provides a ‘SIM locked’ status on the screen. If you are an AT&T subscriber, you can call AT&T and request an unlock code (tell them you are looking at vacationing out of the US and you want to be able to use foreign SIMs). If you are not with AT&T you will need a 3rd party to unlock the phone. I found a seller named ‘nckzone’ on eBay that will unlock the Focus for $5.80. I forwarded the seller the information requested (IMEI, carrier and phone model) in an email and I received my unlocking code in about 10 minutes. This purchase was made at 12:30AM EST, so I am pretty sure the seller is not in the US.
With that, I now have an unlocked Samsung Focus working on T-Mobile. For $50/month I have unlimited voice, text and 2G data- quite a bit less than the $115/month AT&T wants for unlimited voice, messaging and 2GB of 3G/4G data on their contract plan… (granted they are subsidizing a phone, but over two years that is a $1,560 difference).
If you are overly paranoid or hate credit cards you can even keep the prepaid phone as a total cash endeavor by purchasing the refill cards from Target/WalMart/etc.