Usually the caller identifies himself as "Moses" mocking the old testament saying that they "saved" the person from the conversation.
You: (In your head - Fuck! I don't give a shit! How can I leave without being rude?)
*Your cell rings*
You: Oh sorry I have to take this
Caller: Hey, guess who it is? Moses, your fucking savior
You: Haha thanks for that Moses Mobile man, I owe you one