Claudia-Marie does "phone" all the time on Streamate when she's doing webcam shows. The guys on the other end input their number, she puts in hers. Then the phone call is handled anonymously. Neither side sees the other's phone number.
I'm assuming that's what you're doing? That way only current members can ever call you.
Anyway, it's not exactly "new" to the industry as I just pointed out. It's being done right now on Streamate by such pornstars as Sunny Leone, Claudia-Marie, Natasha Nice, Jill Kelly, Jayda Diamonde, Sierra Sky, Diamond Jackson, Devon Michaels, Little Lupe, Ashley Steel, Nikki Nova, Zoey Andres, and Gina Lynn...
Hell let me put my damn code in here to check out the pornstar section:
http://www.streamate.com/webcam/porn...77&UHNSMTY=303
And what the hell....might as well spam my webmaster referral code in case you want to promote them. It's Money Tree that owns Streamate:
http://wm.mtree.com/webmasters/ref/?341477
And all of those pornstars are doing "phone" at the same time they are doing the cam show.
Edit: And doing phone with them in chat doesn't cost any extra to the customer either.