Yasglas

Had the gsm sim no real issues with speed. Used maybe half of the 100mb a month for around $6 a month

Rush2112

After all the BS I went through, basically T-Mobile is no longer supporting 3G in my area. So I had to go through the process of switching over to AT&T through Audi (Can't do it on your own). I got the 2Gb a month plan which is like $9 a month, and I don't even use a Gig. Here's a future problem -- AT&T has already stated on their web sites they will terminate 3G access in 2021. After that, our MMI's will bascially be useless without a carrier. Nothing from Audi (that I've heard) about a 4G upgrade.

robo_audi

I found that the extra MMI connected features are not worth it. Any phone will provide better info and capabilities (especially w. Google Maps).
One solution that I came up with to bring my 2014 A7 to a more modern standard is:

• T-Mobile Sync-Up Drive (https://www.t-mobile.com/offers/syncup)
  This provides WiFi hot-spot functionality plus car tracking (has built-in GPS). T-Moblie had an offer at one time to get a 3'rd line for free (which I use in the car).
• Google Chromecast connected to a HDMI -> VGA converter, connected to the VGA input (+sound) on the car
• Enabled via VCDS the ability to show video input while driving.

Now I can do anything that is possible with Chromecast in my car, e.g. play music (with nice album display), play videos (though don't really use this). Plus have a WiFi hotspot for others in the car as well. For navigation, I use my (Android) phone and Google Maps with live traffic info. Built-in navigation drove me nuts when trying to enter the destination.

So far this has been a good setup working for a few years.
There is the RSNAV route as well....