How many type of Service desk are there?

Below are the type of Service desk

1. Local Service desk: Which is close to the users ( For example, local Service technical  desk).
2. Centralized : Sllows fewer staff to deal with a higher volume of calls  (For example  Service distributed in vruous location due to business continuty or other various reason).
3. Virtual service desk: Staff are in many locations but appear to the users to be a single team (for example Citi bank helpline ).
4. Follow the Sun: Service Desks in different time zones give 24-hour coverageby passing calls to a location where staff are working. (This is self explanatory but one comman example would be Call center).