That's a lesson to learn- you can't really force them to return you anything as the funds weren't yours.
Once you put your money in a wallet that is being controlled by a 3rd party(it means that a 3rd party owns the private key to access your coins, or you own the coins but a 3rd party have an access to your private key), it totally means that you don't really own the bitcoins.

I really hope that it wasn't a large amount of money and it might be a lesson that we should only use open source wallets in the future, even if we are talking about small amounts, because if we give the access to the wallet to a 3rd party we can't be surprised if we find out that we lost our funds.