I bought my 6s Plus using the iPhone Upgrade Program with T-Mobile as my carrier. Was going through a mock iPhone purchase process to see how upgrading to a new phone would work. I see it says T-Mobile is in-store only for new purchases. Anyone know if this is for upgrades as well? i.e. how does one purchase an iPhone 7 using the upgrade program on T-Mobile (it seems like you can't pre-order online... was thinking you might have to choose another carrier and then 'change your mind' in-store). Thanks!