。
My friends call me Beth.
Literal
Friends [topic-は] me [object-を] Beth [quotative-と] call.
The structure [X]をYと呼ぶ ('to call X [by the name] Y') uses the quotative と to mark the name. A common pattern for nicknames and naming. 呼ぶ ('to call') is the verb; Y is always marked with と.