We're playing phone tag and she wants me to leave her a message?

So this girl I'm trying to ask out, we both work at the same place, I've been calling her but she isn't there (people are often away), left a message to call me back. She called me but I was away. So I called her back and left a message to call my cell number. She called but it went straight to voice mail saying that I should call her and just leave a message.

I want to ask her out. Should I keep calling or wait until tomorrow or ask her out via message?
We're playing phone tag and she wants me to leave her a message?
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