There is not a taxi booking hotline in Beijing.  There are few taxi stations on street.  Sometimes the stress of waiting will drive you crazy.  For people who prefer to reserve everything in order ahead of time, this pre-booking service is what you are looking for.  It is a private transfer from hotel to Railway Station in Beijing.  The service is delivered by an experienced driver from a national car rental company, and an English speaking travel agent staff for backup support.  Price is inclusive of all charges such as peak hour charges, midnight charges, city area surcharge, toll and parking fees.