I'd like to know too! I get so edgy when I know BF isn't here in case things go wrong. I'm sure the nerves will subside soon.
I'm always telling myself that this is just a phone. It won't bite.
And also if you really feel panicking, you can always say "could I call you back in a minute"? I believe a nice serious guy will perfectly understand.
And when it comes to creepy guys seriously, it's not important how you end the conversation anyway. I once was talking to a guy, I knew right from the voice he wasn't ok. I tried my "phone dying" method, he wouldn't let it go. I just said "ok, I'm going to hang up now". And I did.
Just think you can ALWAYS hang up;)