[garytelecastor]

I don't play worship music, but one of my acoustic partners does.
When I was first starting to get into the music scene as a player I went to an audition for a band that played Commander Cody, Asleep at the Wheel, etc.
Now I had never heard of these bands, I was quite young, but I thought I could bluff my way in. So I get up there with the band and we start playing, 5 measures or so in, the drummer stops, stands up and looks at me and says: "I am sorry, but we are looking for someone who can play western swing, thank you for your time." I felt lower than a snakes belly, but it was one of the best lessons I ever received in music. I have never put myself in that position again. He really made it evident that it was rude and inconsiderate of me to waste their time. If I could find the guy today I would thank him. In the years since, when it has been my duty to oversee auditions and hiring/firing, I don't waste time with banalities. It is unkind to the person, and it is unkind to me.
It's music, and music is a very personal ability, so people may be offended, but you have a job to do. If "A" can't fill the position you are wasting time trying to make it work. Be kind, yet be honest. Let the person know that it is not going to work and thank them for the time.