The general rule is that an escort will not text you. It is regarded as being very indiscreet.
Having said that many will text guys who they know it is safe to do so. For example, I get texts from girls who I have met previously but they know that it is okay for them to text me as I have told them so.
What does concern me is when I receive a text from somebody who I have not met in the past and who I have not contacted by phone. It has happened to me where I have received a text out of the blue purely with the intention of me booking an appointment.
Obviously numbers are being shared. I can understand this from the point of view of safety etc. but not from the point where it is used to try and gain business. I would say this is far from the norm but it has happened!