Hi Seleranda,
EXACTLY the same thing happened to me! When I started out, I didn't want to invest any money buying a work phone, so I put ads up with my personal number, thinking that when I deleted the ads, my number would disappear from Google listings.
You have to contact Google themselves, as the site you advertised on has no control over Google listings. Here is a link to the Google page I used: https://support.google.com/webmasters/answer/164734?hl=en (mods, sincerest apologies if that's not allowed).
Once i'd done that, the listings were gone within about a week or so. This was 2 months ago, and I placed over 100 ads on 20 different sites, and I can Google my number with absolutely no results, so it definitely worked
Regarding whether you should get a work phone - YES! Mine's a crap little pay-as-you-go one, and it cost me the grand total of ?9.99 plus a tenner to top it up. And as I pretty much never make any calls or texts, only receive them, I spend less than a tenner a month on top-up.
Really hope this helps, as I was in the same position and I know it's scary! PM me if necessary.
Luna x