Originally Posted by WillCAD

I'm not very savvy on this particular issue, but it's my understanding that some carriers will allow you to purchase unlocked phones elsewhere, and activate them on their network. So long as they're compatible technologies, many carriers will activate the phone on their network without any grousing. I suppose this may be a byproduct of the whole, "we lose money on a subsidized phone" issue.

My one experience with this was on Verizon; I bought a substantially discounted Verizon phone from a vendor on eBay (discontinued model and the vendor was trying to clear out their stock). Verizon activated for me on my existing line, with no extra fees and no contract extension required.

I've also met people who bought unlocked international versions of some devices that were not available in the US yet, and had them activated on US carriers. It's not illegal, it's not against most carriers' terms of service, and there's nothing shady about it, so long as the carrier allows it.

So check with the carriers you're considering to see what their policies are toward unlocked or third-party-supplied devices. They may allow it, in which case it opens up more device options for you.