Easy advice - do not use girls from ANY agency or MANAGER in Dubai. Only use someone you know is an independent escort. You will save your self frustration and money.
1.) Agencies and pimps in Dubai almost NEVER send the same girl you saw in the pic even though they promise they will. Either the pic was a fake and she does not actually work for them at all - or they will send the girl who they WANT to send. This happens EVERY TIME. Seriously.
2.) Agencies and pimps (especially the Asian ones) do not share any of the fee with the girls. They tricked the girls into coming to Dubai then they take ALL of the money they earn claiming that it is to repay the cost of the visa and the plane tickets. These girls come from Pacific Rim countries. The tickets and the visa together didn't cost $800 US. These girls will work for 6 months or more for no pay believing they are paying back a much larger amount. This is actual Human Trafficking. Don't get involved in it. The girls will always ask for a gratuity at the end because that is all the money they will get from the encounter. If their Managers and Pimps find out they have it - they will take that too. Don't support those people.
3.) Independents may charge a bit more but in the end you will pay about the same. You can find verified independents on the web very easily. All the money you pay goes to the girl herself. She owes none of it to anyone. So gratuities are not normally necessary since she is keeping the entire fee for herself and after all - she earned it. Nobody is holding her in Dubai to pay off a fictitiously large debt. She is there of her own decision and she is meeting you because she chose too, not because she is being forced too. That is not human trafficking. You can still get in legal trouble if you are caught but the charge for soliciting a prostitute is far less severe than Human Trafficking which is a huge United Nations issue now.