I currently have T-Mobile + a Samsung Galaxy avant ( http://www.gsmarena.com/samsung_galaxy_avant-6542.php ) I want to upgrade to the Galaxy J7 ( http://www.gsmarena.com/samsung_galaxy_j7_(2016)-7870.php ) For my current phone, it says the SIM type is Micro-SIM. For the J7, it says Single SIM (Micro-SIM) or Dual SIM (Micro-SIM, dual stand-by). So that means it should fit since it takes Micro-SIM, that's good. I will buy this one: https://www.walmart.com/ip/T-Mobile-Samsung-Galaxy-J7-Prepaid-Smartphone/54083216 (if it has a prepaid SIM in it or something, I will probably just throw this out) Will I simply be able to stick my current SIM card into this one and everything will work? I don't need to go to the T-Mobile store or anything? One last thing, in the comments section, someone says it is Nano-SIM. I don't think GSMArena would mess this up, but could it be a chance my current SIM wouldn't fit or does this guy not know what he's talking about?