There are plenty of phone ringing sfx out there. You could buy a quality one on Pond5.com for a few bucks probably, or go to freesound.org and grab one for free under the Creative Commons license.
Save as a wav. file and insert into your NLE where appropriate.
It's a ringtone.
No one's gonna care unless the phone is a central character to the story.
FWIW, pretty much anything that isn't PUBLIC DOMAIN is copyrighted; audio, video, or text.
An oblique legal loophole is FAIR USE, which is pretty much only good for making a mockery of the the original or some extreme artsy fartsy application.
Think Warhol's Soup Can or of the SCARY MOVIE franchise.
I think i have got a new site recently to make my own ringtone which includes my favorite name in it. It can mix our favorite name in our favourite song and make itas our ringtone. And the best part is its completely free.
I made my own "ringtone" using Garageband. Just played a few notes and exported it. It actually sounds pretty good and only took about 20 minutes or less.