Last time when I upgraded to my phone, I did it at Apple Store, and I don't remember it giving me a variety of phone plans, so I just picked one. And of course I over paid. So today I changed the plan to a cheaper one and one that suits my need better.
"Fun fact": changing plan (with Verizon) does not affect your contract term.
And if you want to upgrade your phone before the contract ends, you have to buy out the contract first. So annoying. So your phone pretty much sticks with your contract.
So I guess I will be waiting for iPhone 7G! ;)