New Account or use Buying Account? phone number error

I’ve been searching and searching – ultimately trying to find the official Amazon documentation to confirm claims I’m reading.

My situation- I’ve had a personal Amazon account for a long time like most people. I had signed up for a seller account in 2010 and never ended up using it. That email is no longer associated with my account yet I can’t create a seller account with my login. I submitted a ticket to support but their response was useless and without access to seller central you can’t reply to the same ticket.

Meanwhile I’m seeing the majority of people claim to not use your personal buying account. So I tried creating a new account, but I’m getting a message saying the phone number is already in use (it is on my main account). What’s the official policy regarding owning two accounts? I could use Google Voice, but my address would be the same and I don’t want to run into issues down the road…

This seems like the most simple thing. But losing access to your account would be stressful once you get business going (have read a bunch of reports of this).

Can anyone help point me to official Amazon policy docs? Any advice on how you handled what seems to me the most common situation?