Thanks for the info. It will be an upgrade. I'm happy I can avoid the retail store!A nano sim is included with the phone. It should automatically switch you to the sim when you activate the phone if you are upgrading. Otherwise, you can change your sim on the mytmobile website, under the phone tab. Choose the change sim option on the right side of the screen. You just need to type in the new sim number and T-Mobile will automatically transfer your number to that sim so you can use it with the new phone.
I ordered mine direct from tmo and got it wed. It had a sim card enclosed. (The select-a-size card). I did not use it. I pulled the nano sim out of my iPhone 6splus and popped it in the 4s. No problems with the cell service. I plan to swap back and forth as needed. I saved the sim for another day but it does have an expiration date on it for 2018 or 2019.If you order the phone online, and you're not already using a nano sim, I assume you have to go to a retail store to get it setup? Or is there a way to do it online?