I am looking to get my mom a smartphone for her birthday and I've decided to get the Moto G (2nd Gen) and I saw on Amazon that the US GSM version will take 4-7 Weeks to ship while the Global GSM Version will take 2 days with prime. I was wondering what the difference between the two are and if with the Global GSM version she will still be able to use her ATT plan and make calls and text like normal. All help will be greatly appreciated!