I went to an incall service and the provider was great. A true GFE! After the session as I was leaving she asked for my business card so she could call me. What should I make of this?

You never know, JM. I would've casually asked why, but that's Monday morning quarterbacking. I just think if her place ever got raided, they don't need my card in her purse or house...in other words, tell her, "Don't call me, I'll call you."

Simple marketing.  She wants to keep in contact with you so you will come back and see her again.

ah marketing!

Saw her again and she gave me her number both home and cell.  Called me and left a voice mail (on cell) asking me if I wanted to go with her to hear a band.   What do you make of this????

Maybe she just likes you,and feels that the two of you hit it
off fairly well.What the hell.....go out and play with her.This could be a good thing.
If you're single and don't mind being seen with her,go for it!  

Yes, tell her you would call her, or give her your cellnumber or email if she wants to be something more than business with you... let's say she likes you......
I dont think you should give her your businesscard