When there was a federal government, these problems were easier to solve. Since the FCC is mainly shut down now, the solution is not as simple.
The FCC takes complaints, both on their web site and by toll-free call (neither can be used right now) for wireless carriers. If your new phone solves the problem, great, end of story. Live happily ever after.
If the new phone does not solve the problem, you politely thank the Verizon rep, and take their name and position down. You then open a complaint with the FCC. Within two business days the Verizon Executive Offices will call you back. (Similar from all carriers, pass the word around.) Every time a complaint is filed, they get a demerit. When they ask for rate hikes, someone opens the folder, says "Eh, too many demerits, no hike for you!" so the carriers have a real simple incentive to CLEAR THE COMPLAINT. And if they do something silly like reply it has been cleared--but the problem is still happening--more demerits.
The contact from the Executive Offices is the *only* support person at Verizon who will be allowed to talk to you about anything. Your file gets red flagged as a hot potato. And the XO rep? Actually has the power to do whatever is needed to fix the problem. If the problem is some mystery in Pixel3 phones on their service...Yes, they can replace your phone with an S9 or any comparable phone in order to try fixing the problem. Or to simply refund your purchase, take back the old phone, and make whatever other arrangements work.
In some states there is a State Utilities Commission or other office that also regulates wireless carriers as well as landline, but the FCC has authority over all wireless carriers, in all of the US. And they seem to scare the daylights out of the carriers when they say "A complaint was filed...".