You must buy it designating T-Mobile as your carrier. They require 40 days of service, again per USA Today, at which time you may remove their SIM card, they will unlock the phone, and you can then put in whichever carrier's SIM card you like. . . So long as the radio is compatible with that carriers assigned bands. Most likely it will as the iPhone 6 is compatible with 27 systems and bandwidths. But, Dino, there is no way, since the release of the iPhone 6 to walkout with an unlocked one. You can only buy an unlocked iPhone 5s or 4s directly from Apple at this time.
This means your friend did not buy a pair of iPhone 6es to take back to Jeddah, as I told you in the first place.
The one workaround is a contract Verizon phone, which has an unlocked sim slot. Pay the ETF and you technically have an unlocked GSM phone.