This is an excerpt that I wrote for ebaY on mobile phone

Carrier Specific vs. Unlocked Mobile Phones

Many mobile phones (and PDA and smartphone devices) which are for

sale on eBay are phones which were purchased through North American carriers. The largest North American Carriers are Cingular, T-Mobile, Verizon,

Sprint Nextel, and Rogers wireless (Canada). In NA, these carriers work with the handset manufacturers to “lock” the devices so that they only work on

each specific carrier network. This practice of restricting the phone provides some security to the carriers, and they sell the phones at a subsidized

price to the consumers figuring they make more money by locking consumers into long service contracts.

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