Most probably, travel agents, specially the ones who provides services like hotel reservations online, must be one of those who use telephone for most of their business activities. Though the big travel portals or travel companies have call centers which operate 24 hours a day for handling right from inquiry to ticket booking as well as hotel reservation. But there are many small and medium travel agents which have good web presence, but can not afford to have a call center, or can not operate office 24 hours a day.