iPhone Upgrade Program Eligibility

I have used this program as an affordable means of acquiring the latest iPhone since I purchased an iPhone 7 Plus in 2016. Now that the iPhone 15 models are available, and I am eligible to upgrade, I was very interested in getting a 15 Pro Max. But there's a hitch.

Last spring I switched carriers from one of the "big three" to an MVNO because it gave me significant savings on my monthly cellular service bill even after an introductory rate. When I attempted to order a new 15 Pro Max through the Upgrade Program, I found that that I am no longer eligible to participate in this program because I am not a customer of one of the big three companies.

I am very disappointed with Apple over this policy. Unfortunately, I have decided that there will be no more new iPhone purchases for me until this changes. All iPhones now have eSims, so how difficult can it really be use allow your customers a better range of choices among carriers?