Recently I had an experience with a provider (I thought independent provider) that pulled bait and switch....I asked her to leave... but left two thoughts:

1) I would never call on her again
2) This wasted both of our time....

so, I ask providers who does this frequently, why?????

I'm no provider (duh) but it happened to me a few times before I figured this all out.  One time the girl was okay so I let her stay, another time I sent her away nicely and the third was a hotty but was a ripoff.  I talked to the first two about it and they said that they don't like it either but they don't have any say over it.  The agency tells them where to go and is counting on the customer to be too drunk or horny or short on time to care so you might take the girl anyway.  These girls aren't usually attractive enough to get your attention in an ad but might suffice if she's standing right in front of you.  The big warning light should be flashing if she is different but still hot looking-- that is almost always a sign that you are about to get ripped off.