But if you purchase a phone from Google Play Store it comes without any contract or anything. And you dont break your contract with your carrier, you just switch to a different phone on the same contract.
Which is a breach of contract. My mum tried that when her phone died (which was still in contract) and got a new phone and our carrier sent her a message that either she go back to using the old phone (that was contracted to her) or pay the early termination fee for breach of contract (we explained what happened and they wavered the fee and re-contracted). I have no idea how they found out, maybe the SIM card is locked to the particular phone and they know when it's switched to another phone? no idea. Either way, rather not risk it.