function raiseDispute(uint _transactionID, uint _arbitrationCost) internal {
        Transaction storage transaction = transactions[_transactionID];
        transaction.status = Status.DisputeCreated;
        transaction.disputeId = arbitrator.createDispute.value(_arbitrationCost)(AMOUNT_OF_CHOICES, arbitratorExtraData);
        disputeIDtoTransactionID[transaction.disputeId] = _transactionID;
        emit Dispute(arbitrator, transaction.disputeId, _transactionID, _transactionID);

        
        if (transaction.senderFee > _arbitrationCost) {
            uint extraFeeSender = transaction.senderFee - _arbitrationCost;
            transaction.senderFee = _arbitrationCost;
            transaction.sender.send(extraFeeSender);
        }

        
        if (transaction.receiverFee > _arbitrationCost) {
            uint extraFeeReceiver = transaction.receiverFee - _arbitrationCost;
            transaction.receiverFee = _arbitrationCost;
            transaction.receiver.send(extraFeeReceiver);
        }
    }