I just think a phone conversation is more straight forward and to the point. With texts you can't discern emotion...and over the phone you can at least hear her tone of voice. I think that if you had called her in the first place about your next date...then you wouldn't be guessing so much still...
Texts get people in trouble sometimes...so as a general rule I think that in the initial stages of dating hearing someones tone is just easier and leaves less room for guessing.
It's up to you thought of course. Whatever you are more comfortable with. I make it a rul not to text about anything when emotions of any kind or any level are involved. In person is always best, but over the phone is next best.