Indigo Airlines — lost my husbands new mobile

Address: Kollam, Kerala, 691021

While travelling from trivandrum to chennai on dec 4th 2017 at night 8 pm flight my husband lost hisn new expensive phone,
I have filed fir and complined twice to indigo itself.
It was lost while in flight. Samsung galaxy edge.
I have all the details of the same including the cover.
Imei no is [protected].
Whom should we contact again.
We are terribily feeling dejected with this attittude.
So kindly look into this and do the needful.