I contacted with unipay and they told, that only have to get BTC, they can not get BCH, because of this they can not help - is it correct answer? or they are lying?
Who can be given me private key?
Thanks
Well unipay has the private key for your transfer, so you could always ask them if they can give you the private key for the transfer that you did to them.
Otherwise there is no hope, or if they are not working with you, you could always fill a scam accusation. However, you were supposed to send BTC and not BCH, so it is kind of your fault as well.
However, if they say that they cannot access the private key of the address, they are lying then because the private keys are same for BCH and BTC.