The voice lines didn’t land strongly for me. At first I didn’t understand what they were. Once I realize it was the package owner, they felt less impactful than improvements to core gameplay would be.
I'm not trying to discourage you from having voice over though. There's definitely room for flavored voice over to provide some feedback on the success/failure of the delivery. It seems like hearing the package owner is something you probably wouldn't experience as the player since you're on this mad tear to destroy and deliver as many packages as possible. The delivery person wouldn't be waiting to hear what the package owner says, but I might be thinking too literally.