UniverCell store, Velachery, Chennai — Micromax + Photon + bundle offer

Address:

Chennai, Tamil Nadu

I bought Micromax funbook from Univercell store, Velachery, Chennai. Funbook has bundle offer with Tata photon+. It mentioned that they will offer Photon+ for additional of Rs 500.

But in Velachery Univercell store, they mentioned that the offer is not valid in Univercell and they charged Rs 999. One of my friends bought in Croma store and he availed the offer.

The response given by store manager is that they sold 1008 (standard number) micromax and they didn't offer to any of their customer.

Is there any way to recover my excess amount?