OK so it's not life and death stuff, but all you really need to say is: "Sorry we're not here, please leave a message" or similar.
NOT: "Sorry X, Y and can't take your call at the moment, but please any messages after the tone. Alternatively if you'd like to call us on our mobiles, X's number is blah blah blah, and Y's mobile number is blah blah blah. Thank you for calling and we'll get back to you soon. "
*including babes in arms who don't even know what a fucking phone is.
Keep it snappy. My time is precious.