、、。
Hey, you — make the reservation.
Literal
Hey, you, reserve-[rough-imperative-てくれ].
Abrupt and borderline rude. おい is an attention-getter used in rough speech (contrast with あの). きみ ('you') can be friendly among peers but becomes condescending when used toward someone the speaker doesn't know well, or by a superior. してくれ is a rough imperative of してくれる — 'do it for me' with no politeness softening. Useful as a calibration point for how blunt casual Japanese can get.