Q: Can I connect an iPhone 6s

If the iPhone is not locked to another wireless provider

and Boost Mobile supports your particular model of iPhone.

Sim free is not the same as unlocked.

What did Boost Mobile say when you contacted them?

Info might even be on their website.

Depends on where you purchase the iPhone?

What retailer in what country?

Have you checked with Boost Mobile to see what models

-if any- of iPhone they support? That would be a good first

step to be sure you can get an iPhone that will actually

work on Boost Mobile.

Buy as sim-free. http://www.apple.com/shop/buy-iphone/iphone6s#00

Get your sim from Boost Mobile since it is not an option on Apple's site.

Perhaps I am mis-reading your posts, but you seem reluctant to

contact BoostMobile.

Their website shows they sell the iPhone 6s. I leave it as an exercise for

you to determine if they will accept one on their network purchased

from another source.