unlocked

CNET reports that Verizon has announced that it will no longer sell unlocked smartphones in order to deter theft. From today, all Verizon devices will be locked in to the Verizon network, but only until the customer signs up and activates their service, after which they will be unlocked...

I'm travelling abroad for a few years, but reside in the US and want to purchase an unlocked iphone 6 or 7 in Singapore that will also work in the US (I'm already in Asia so won't be able to purchase in the US for a while). Are there particular specs I need to look for? Wondering how it works...

My Verizon iPhone is unlocked, I want to use this phone with T-Mobile, but I have heard that you only get HSPA+ which is mediocre at best, the iPhone supports 2 out of 3 LTE bands that T-Mobile uses, will LTE work?