Let Me Know if You’re Down
This person wasn’t “down” with working for free, and we can’t blame him. We don’t have enough context here and we’re not sure what kind of service this person provides, but whatever it is, there’s no reason why they should work for free. There’s no reason why anyone should work for free unless they’re doing so for charity or helping out a close friend.
Of course, this person was offered Instagram exposure, which in different circumstances could’ve been worth a lot. However, 300 followers are not enough to create any kind of meaningful exposure for a business or an artist, as this person understands. So they had to respectfully decline.