Do you already run an audit on your phone to look for a potential malware? There’s a lot of same issue like you with Coinomi especially wallet with huge amount of Bitcoin that dormant on there wallet but since Coinomi is a non-custodial wallet, its very hard to accused them stealing your money since you are the holding your private key. Jut follow there suggestion to report this to law enforcement so that they can easily request files the company that received your Bitcoin.

Invest on hardware wallet like trezor and ledger next time if you are holding huge amount of Bitcoin to a none open source wallet. Sorry for your loss mate.