Do escort agencies make the escorts charge additional fees besides the one listed on their website before any "activities" are done ?

Because I heard the fee listed on the websites are just a fee for hiring the escort to come to your outcall location. Then more money is charged before any "activities" are done.

Do your homework ahead of time by reading the reviews of the providers and/or agencies. Try to become a VIP on TER if you can. The detailed reviews here will provide a lot of information prior to your encounter. Good luck.

That is what is referred to as upselling. Yes, some do that, you definitely want to stay away from them, usually end up being a ripoff anyway. As already mentioned, do your homework and check reviews, some agencies also advertize 'all inclusive' which should help alot.