Lumia 950XL SIM card

[Windows Central Question]

I just noticed that the Microsoft Store has the 950XL in stock again! YAY! I pulled the trigger on one immediately. It should be here next week. Now I'm going from a Lumia 920, had it 3.5 years longest I've ever had a phone was a iPhone user before that; anyway I know the SIM cards are different.
My question is can I just log into my ATT account and order a nano sim card for phones? I'm currently looking at the webpage and it states I have to enter in a IMEI number, now following the 950XL as I have I recall reading about some LTE issues people were having and they were giving IMEI numbers from other phones.
So my next question is can I just type in the IMEI from my current Lumia 920 and order the nano sim now so I can have the sim card by the time my phone gets here? Or is the afrementioned issue resolved and I should just wait for the 950XL and type in its IMEI?

Thanks for the help guys/gals.

 

[MrEeks]

Bump for an answer. I'm the OP didn't realize I was not signed in. If I do order a nano SIM with my 920 IMEI, is my current phone going to be disabled once I submit the order? In which case I should wait until it arrives?