In the US, you cannot switch. 2019 models use AT&T and 2021 models use Verizon. My E tron is a 2019, so the hotspot I am using is AT&T. My mobile phone plan is Verizon. Actually, AT&T coverage is a bit better around my home than Verizon, but I am sticking with Verizon for other reasons. Now, since I am on Home Wifi (Xfinity) when at home and on the Audi AT&T while in the car, I found I could cut my Verizon data plan to the bare minimum, given that when using data I am mostly at home or in my car. What I saved on reducing the Verizon plan almost makes up for the Annual Unlimited AT&T subscription available in the car. I'm finding I'm still barely using any of my Verizon data.