Trivial if you have access to an SS7 network that has a direct access or a roaming agreement with the network of the victim, and the proper tools to do that. But you will not manage to do it within 2 minutes if you have.
I was thinking of someone just walking into their local cellphone store and sweet talking the person behind the counter to transfer their number off of their old "broken" phone.
You are thinking about it from the wrong angle. Even less than 2 minutes.