OP sent funds to this account knowingly or unknowingly that it is Naster partner account which means Naster is fully responsible for the funds. There is no way to chargeback these funds. (At least if it was in € and SEPA bank transfer)
I understand. But, since Naster Claims that the fund wasn't released from OP's bank. OP can provide proof that the fund was released. I know that the bank will never keep the funds. Either they will ask for some proof from the receiver or they will return the fund where it comes from.
I know Naster is lying, but, I guess this is the only way to prove that the OP has released the fund from his bank. Also, OP can ask his bank to make sure if the fund was released or not. I guess he already did. But, I am saying in case he didn't.