To fix your credit history, take out a small Bank loan which does not make requests to the credit Bureau. These banks are really a lot, so if you put a little more effort, the search will be successful. After approval of loan application, try to dampen it a little ahead of schedule for a few days. When you pay the full amount, your credit history will improve, and banks will be more willing to cooperate with you.
Can go into any Bank and write a statement to the security service. Your application will consider, but you should not rely on a large amount. You, if approved, will be given minimal credit for the maximum percentage. But be patient, next time will give you a loan under the General lending conditions.
Also you can make contact with the same Bank that you owe money. If your problem will be reconsidered and you will pay the debt, you can edit the credit history. But that's not all the banks wish to communicate with the debtor, but try still stands.
Do not contact any agencies that promise to fix credit history for the money. The payment they will take and give guarantees, but only credit history will "forget" to fix it. Unfortunately, other legitimate ways to fix it are only a few, and the rest of the round.