Does she know that you like her that way? Maybe she thinks you are kust a guy friend and you don't care what she does. So now you have to tell her how you really feel and that it bothers you that she talks to other guys on the phone, or you just can't say anything if you don't want to tell her how you really feel about her. Hope this helps.
I think you should tell her you like her, and if you guys date and she talks to other guys on the phone you can tell her how you feel very uncomfortable with her doing that. But just warning you, don't say it in a way which tells her you don't trust her to talk to anyone. :) good luck! ;)