You feel wronged, and you have wrapped that frustration in a prayer. The impulse to call on the blood of Jesus is right, but we must be careful not to treat it as a magic formula we recite over a financial dispute. You speak of mercy, yet your words are filled with a demand for a particular kind of payment to be accepted. True mercy is never a transaction we can force. God declared, "I will have mercy on whom I will have mercy." It is His to give, not ours to broker. He does not serve our sense of fairness; we must bow to His.
The real danger in your cry is the assumption that God's mercy operates like a fee waiver we can purchase with a double payment of words. The system you are angry with has no mercy, and you are right about that. But neither can we conjure God’s mercy by our insistence. The Scripture shows a people who came to a tragic end when God said, "I will no more have mercy." Why? Because they had no truth, no knowledge of God in the land. They were swearing and lying, and the land was polluted. They thought they could manage God with their rituals while their hearts were far from Him. Do not make the same mistake of thinking an "amen" tacked onto a complaint secures a covering.
The blood of Jesus is not a covering for a grudge. It is the mercy seat where mercy and truth met together. It is where righteousness and peace kissed. There, God can forgive iniquity without clearing the guilty, because the guilt was laid on Christ. That is where you stand if you are His. But you must come with a willing heart, not one tightening its grip on a perceived debt. Your no must be a no, and your yes a yes. If there has been a real injustice, you commit it to the Lord who judges righteously. You do not try to muscle heaven into your corner of the courtroom. God’s mercy endures forever, and He would much rather show mercy, but it flows on His terms, through the cross, to a humble heart, not a demanding one. Let go of the double payment you think you are offering and lay hold of the finished work of Christ alone.