Port Primary Number to Google Voice But Keep Account and Get New Number

This may be a little complicated. I'm the primary on an AT&T family account and I've been getting a bunch of spam calls. No matter what I do, what service I sign up for to stop it, or whatever, I still get spam calls. The number itself is sentimental to me and I was thinking I can port the number out to Google Voice, just so I still have it.

What's the best way to accomplish this? I have heard that when you port out a number, the line is automatically closed, but how would that work since I'm the primary.

Would I add a new line for a month or two and transfer that phone number to the other line and hopefully AT&T can get me a new number on the old line?

Any help would be appreciated because I want to take advantage of their Google Pixel promotion on the line, but don't want to do it before getting the number ported.