I tried one and totally put me off. Be very very careful. Most photos are fake. They will charge you a basic call out fee of 180 and when they arrive will ask for an extra 100 just to kiss and oral without. Even the massage will last 20mins.
Just get as much info upfront as possible. Sometimes the agency will say sorry we cant discuss about extra services. Say fine, I want to discuss it in advance with the lady herself. Then get all the info upfront. If you do these steps then you should be fine with most agencies.