How can I track who is following me or hashtagging something?
 

I work for a party hire business based in Sydney, and my boss has asked me to send out a promotion to our mailing list offering everyone 10% off if they follow us on social media (or maybe use a certain hashtag if that's easier).
The problem is, I don't know how we can verify who is actually following us to give them the discount.

Please anyone suggest me how can i track who is following