Carrier iPhone Upgrade Program for use with employer owned SIM

All, I was hoping you would be able to help with a particular challenge I have coming up.

My employer has provided a 16gb iPhone 6 which I use as my primary phone. It is a little small and old at this stage, but an upgrade isn't likely for a few years.

I would like to purchase my own iPhone and swap the SIM between my company phone and my personal phone. (let's ignore any potential policy issues with this).

Given how much I like staying up on the currrent tech, I wanted to sign up for the iPhone Upgrade Program to allow me to swap out the phone every year. Earlier in the week, I was testing out the ordering system on a iPhone 6S to understand what is possible. The ordering process continues to ask for a carrier / account info even though the phone itself should be unlocked (I believe). This is a problem, because I don't have access to my account and ability to provide the required details given that it is a corporate plan.

So two questions:

1. Is it possible to sign up for the upgrade program without having a personal account?
2. If not, what is the cheapest, no contract, way of aquiring an unlocked phone, with the intent to then cancel the service?

 

Hmm - makes sense. Then the related question becomes very relevant:

Which carrier has the cheapest plan?

• E.g. cancel immediately and avoid any monthly charges
• E.g. keep for a single month, at lowest total cost (monthly fee + activation)