I think using the phone could be interpreted as not “owning” your stutter and be initially unappealing to girls and other people you meet for the first time. If your stutter is really severe especially in those kinds of situations I think using that as a backup plan is a solid idea. I think that the last point you made says it all though, girls who you get to know more won’t view your stutter negatively, which I’m learning myself in college. There’s not as much to fear as we think there is. Not to say the feelings of helplessness at times aren’t severe