"Sim Not Valid'' International Solution
IF you have verified that your phone is “carrier unlocked” and you are still having problems. This problem is still going on and relatively unknown until people experience it. It appears to be an issue with iPhone 6/6s models that were offered as "Service Replacement" phones by Apple and assigned an "incorrect policy" from Apple's servers. (See below.) The error occurs when the Apple Server tries to validate the iPhone's IMEI number, there is a lack of synchronization between the databases of Verizon Wireless and Apple servers.
The phones will work with U.S. domestic carriers but not with international SIMs when the user receives a "SIM Not Valid" alert.
If the Apple Customer Support person you talk to is uninformed of this issue, tell them the phone is not locked according to FCC guidelines and there is no pending contract with any US carrier. What needs to be done is to escalate the case to a Level 2 Support Technician or a Senior Level Advisor who will agree to forward a request to Apple's engineers who can fix it from their side. This is the only way to fix it by getting the "activation policy" corrected by Apple engineers. Email your Apple Customer Care Representative a direct link to this post and it will help you as it has helped others to solve this issue for you.
When properly identified, Apple will tell you that you have "a replacement device with an incorrect activation policy" (which takes 30 minutes to 24 hours for engineers to correct). Sometimes the iPhone needs to be restored after Apple makes the change to the activation policy for the phone, before it will work with an international sim.
Most people who have run into this issue get stuck in a loop where Apple tells them their iPhone is locked to AT&T or Verizon. (Yes, we all know Verizon can not legally lock phones.) AT&T or Verizon will accurately say the phone is not locked to their servers. The result is a frustrated phone owner. Unfortunately many find out only when they get overseas.
The SIM Free iPhone "appears" to be locked "internationally" when in reality it is an Apple server setting that essentially acts like an international lock. It can require quite a bit of patience to be nice and persistent with Apple Customer Care Service, and repeated calls/visits to find someone who is open to the idea, since it is an obscure problem relative to the number of total Apple customers, but a large problem for those in need of international phone use. "Service Replacement" iPhone 6/6s iPhones appear to be identified by model numbers starting with an "N".
Should someone plan to use the phone internationally, or want to get more value upon resale, it would be wise for anyone who has received a replacement SIM Free iPhone 6/6s to check their phone. This information is also good for future buyers of iPhone 6/6s who wish to use the phone internationally. There have already been cases where honest owners have sold their phone, not knowing it would not work overseas when the buyer has expectations of it working globally. Neither party is typically at fault, since the SIM Free 6/6s iPhones are promoted as/and are unlocked to begin with.
When contacting Apple Support, it is strongly recommended to provide the AppleCare+ work order created during the "replacement" and the "order number". This will ensure that the "replacement phone" has the same “activation policy" as the original phone to ensure that all International SIM's will work. Receipts from your original phone prior to the replacement might help also.
The policy for the phone to work domestically and internationally should read:
US Verizon LTE MM N61/N56/N51/N48/N42 = Fully Factory Unlocked for U.S. + Worldwide Use
As opposed to something like:
US GSM/VZW N61/N56 Service Policy = Unlocked Domestically / Locked Internationally
Good luck.
