I want to get texts about my bill and payments, but I can't enter a Google Voice # to do it.
Amazon can send me texts on that number without any problem.
You are asking peers here. As far as I know there is no problem adding any phone number in the U.S. Does it give you some sort of message, e.g. telling you it is not a mobile number?
The "Contact Us" link refers to me the forum to ask questions.
When entering a Google Voice number as the mobile number, it indicates it is not a mobile number.
The site doesn't distinguish between a mobile phone and text phone number.
There doesn't appear to be an "email" option for support any longer, so I tried posting on Twitter to the Verizon Support area and here. Hopefully, someone who is actually in the right area will apply and consider changing how this information is handled.
Verizon's official support channels are through phone and chat. They don't do email support.
The "Contact Us" link will give you the phone and chat options, plus the forums. Verizon doesn't do as good a job as I'd like explaining that the forums are primarily for peer-to-peer support. We "Community Leaders" remind them of this when given the opportunity. In the meantime, we all have to follow Verizon's rules and procedures, as this is their sandbox.
Verizon does have folks who monitor social media including these forums, Twitter and others. It's up to them to decide if an issue will be escalated to their support team.
Your question about Google Voice numbers may or may not be noticed. It doesn't appear to me to be a simple support question as it most likely involves the infrastructure of telephone numbers. To do what you want will most likely require changes to their systems and may involve systems at Google as well. In other words, it's most likely not as simple as changing a setting on your account.