Wireless Network Gurus?

I've been an unwilling student in cell networks the past couple of days.

Phone: Pixel XL
Carrier: ATT

Source problem:

Incoming calls were being sent straight to voicemail or ringing the full time and being sent to voicemail. Both types of calls would not be indicated as "missed" with the only indication being if a voicemail was left.

Outgoing calls would take 10-15 seconds to connect (start ringing).

Cue tech support by Google and ATT.
Lots of cleared caches, tweaked settings, new sim card... Bang head against wall... No change.

Through all this data streaming was not noticeably effected. Videos, texts, etc acted normally.

Call issues were also remedied by having a wifi connection.

Then I notice when I called and had issues, the network would go from LTE to H to H+ before connecting.

A Google search lead to information from 2017 that Pixels and Att did not get along and operated mainly on 3G.

So I change my preferred network from LTE to 3G and voila. Calls are normal again.

In all of this frustration, I decided to order a Pixel 3. Newer = more better, right?!

My question to the experts or very knowledgeable is did I find the solution, a work around or temporary bandaid? Is this a known issue no one wants to admit? Will the Pixel 3 be better in terms of accessing 4G LTE.

Of course ATT keeps saying it MAY be because I'm using a non certified ATT device (straight out the Cox playbook).

Id say Frick it and jump back to Verizon, but I'm actually on the First Net plan and pay $50 or so bucks for unlimited data/Hotspot.

I just really don't want to be back in the Samsung ecosystem. I'm admittedly very set on the Pixel 3 because of the fantastic camera, unlimited photo uploads to Google photos and a very slick Android experience.


TL:DR Pixel problems on ATT network. Is there a fix for the Pixel XL (original) to fully access 4G and/or did the Pixel 3 address those issues.