Will an iPhone 15 Pro Max bought on installment plan from USA work in Pakistan?

I believe the US iPhone 15 models all only use an eSIM, not a physical SIM card. You would have to find a carrier in Pakistan that does those.

About region blocks, I have not heard of those. It isn't something Apple does, except possibly if you are trying to use an account set to the USA and are trying to get items from the USA store while in other countries. That has nothing to do with cell service.

If you have problems with the phone, Apple will not repair it except in the USA. Warranty restriction! - Legal - iOS Warranty Document Us - Apple - "IMPORTANT RESTRICTION FOR iPHONE, iPAD AND APPLE TV SERVICE. Apple may restrict warranty service for iPhone, iPad and Apple TV to the country where Apple or its Authorized Distributors originally sold the device."

The warranty does not outright deny warranty coverage in other countries but there are many limitations to the effect Apple almost certainly will refuse to do repairs under warranty or even repairs at all except in the country of purchase. The device would have to be sent to a friend in the country of purchase to handle any repair claims because Apple will not handle international shipping.

Don't forget that USA prices on the web site do not reflect sales tax.

Also do not forget that many countries may impose hefty customs and duty on some items. You may still end up paying more in the end, plus you have all the disadvantages of having a phone from another country.

1. US iPhones only support eSim. In Pakistan only Ufone appears to support them. click here ➜ Find wireless carriers and worldwide service providers that offer eSIM service - Apple Support
   1. Make sure Ufone is willing to activate a foreign iPhone on their service
2. What kind of installment plan are you going to be using? From who?
   1. The Apple Card option of Monthly Installments, will provide an unlocked iPhone that can work with any carrier worldwide. No region lock is applied. However you will be required to choose an American carrier like AT&T, TMobile or Verizon and have active service with them to make use of the Apple Card monthly installments option.
   2. Other installment plans such as those from carriers specifically will result in an iPhone locked to said carrier. This is the case with the AT&T direct installment plan. (Unrelated to selecting AT&T with the Apple Card Monthly Installments, different things, not to be confused).
3. The iPhone warranty will only be valid in the US and any service or repairs will require the iPhone be sent back to the US for service. Apple will not take international shipments for service, so you will need to send it to your sister and she will need to take it into an Apple Store or set up mail in service from within the US.

The iPhone 15 Pro Max sold in the U.S. does not have a SIM card. Please check with the carrier that you plan to use to ask them if they support eSIM.

Please understand that an iPhone purchased in the U.S. will likely have no warranty coverage in Pakistan. If the phone requires service, it will probably need to be returned to your sister, so she can take the phone in for service.

Our general recommendation would be to purchase the phone in the country in which it will be used most of the time.