A greeting and a farewell may or may not be included, depending on the situation as well as the callee.
The most important feature of a function call is the absolute lack of smalltalk. Omitting the usual "so what's up" part makes the conversation brief, effective and usually both less time- and cash-consuming compared to texting.
On the other hand, this fact may render function calling incompatible with most women due to their natural chitchat and gossip requirements.
The name is derived from the programming jargon due to the similarities to calling a function in a programming language, which usually includes specifying parameters and obtaining some kind of return value, close to immediately.
"Nothing important, just a function call from my buddy. He forgot my email address."