OK so clearly ignore boynick as he is clearly advertising an escort service. If you pay for an escort service in Dubai over the phone you are getting the short end of the stick as you will pay much more and there are so many providers to choose from in local bars and clubs. Not to mention the fact that you can never guarantee who shows up at your door, better pick yourself in person!
Only reason I find for escort services is for people who don't want to be seen in those clubs and bars or who want something very "specific" and don't want to take a chance on shopping around.
I lived in Dubai as well as go there often, and the advice given by ausername is spot on. Always ask your hotel about the "guest" policy they have, they will tell you.
Also feel free to negotiate with the girls. They will always give you a high end price (usually inflated about 30 or 40%). Depending on how clean cut you are they will give you a discount as they prefer to spend the night with a good looking guy rather than a slob who will pay only slightly more. But if you have any expensive watch/jewelry, keep them home as they will make them push the price up.
Last time I was there a few weeks back the going full night (usually six hours) rate middle of the week was between 800 - 1500 AED and on the weekend its 1500 to 2000 AED. (compared to escort website prices which are 1500 - 2500 AED per hour!)
Last but not least, keep in mind its still technically "illegal". So when you pick them up you can discuss everything very openly, but once you start heading out of the club, you need to be careful. Just act like you are on a first date, that is the guideline to not offend anyone.
Hope the above helps everyone
Have fun and good luck