What are Robert called?

"Robert" is a name. It's not something that people are "called," it's what they are named.

If you're asking what people named Robert are called, that would depend on the context:

* Formal: Mr. Robert [Last Name] or Robert [Last Name]

* Informal: Bob, Rob, Robbie

* Nicknames: Many other nicknames are possible, depending on the individual.

Do you have something else in mind about what Robert is called?