Good day! How many SIM cards does this phone use, two or one? How to determine if you have an Apple on the site,Do you guarantee full compliance with the original and work with the Apple store ? Whether you are upgrading the system, or will forever remain as installed? What happens if I update it? Reply:its has dual sim card slot. if you need one sim slot version,we can do send one sim version too.it comes with 45days refund or replacement,18month warranty.OS support update autumatically....