1)What is making you think it's another provider? What is it that's bothering you about the email? I would respond as if you are talking to parents until proven otherwise. This would not have even crossed my mind in normal circumstances but if they said something that tipped them off them don't answer them.
2) I like to respond by email because phone calls are not convenient for me but I will call them back if necessary. It's on my website and that's also how I get most of my contacts. So they have already familiarized themselves with most of my basic info.
3) I don't do b/a care.