Ever talk on the phone before an online date?

Yes, it's fairly common with online dating. Women often use it as a screening tool. Verify that you are a real person (people still get stood up for dates), get a feel for how talking to you will go, etc.

If you're going to be doing online dating, expect to be asked that pretty often. When I was doing online dating, for all of the women that wanted to talk on the phone first, it was never a long call. So you'll still have plenty to talk about on the actual date.