The call ...

Today I receved a call from a friend asking me to participate in a religious encounter, but to be part of the organization. I'm in a little bit of a crossroads cuz I don't want to say no, but I really can't do it. So, I don't know what to say.  No matter what I choose I know I'm letting someone down.
That's not me I don't like letting people down! But sometimes we don't have other options....