Visible is only single line accounts so a second number can't be added to your current account. To have a second line you would need another account on Visible in order to run both numbers. If at the end of the month you want to keep your main account you would have to port out the second account or new number to another carrier then I think you should be able to port it in on you current account, not 100% sure on that though.
One thing I want to point out is that most numbers nowadays are recycled numbers, not sure if you can get a guarantee from number barn that it has never been used. For your current number I see a lot of advertising about DeleteMe, maybe a subscription from them for a month or two may get rid of your number for a while online.
One mistake I made a few months ago was when I was in O'Reilly's they ask for my number for their rewards program and what a mistake that was. Two days later I like 15 calls in one day and it has taken the last few months to get it back to one every two to three weeks. I had started with this number 4 years ago and it was new, the spam I was getting was for two of the previous users of the phone number. Make sure your current number is added to the national do not call list. If you are getting multiple calls from one particular business like car warranty I suggest reporting it to the FTC, they have a site to report this two. I had a persistent warranty outfit me, wasn't any use to block them since each time they called the last digits of the phone number were always different and I never got a name, I tried. I still reported the zip code, the prefix and the the first digit that never changed and somehow the spam stopped. I think the last spam call I had was at least 2 weeks ago. The funny thing is if I look up my number online it even shows it belonging to the person I get the spam calls about.
