If the account paperwork/contract says that they can close your account for any reason, then there is nothing that you can do to stop them from closing. But, even if the contract says that you will hold them harmless for the account closing, this can't include if the way they close the account damages you.
Seems to me that you said or referred to something about your credit. If the method they use damages your credit, you need to find the link between the closing and the damaged credit - the report to the credit bureaus - that has caused the credit bureaus to drop your credit rating, thereby damaging you.
Once you have done this, start a letter writing campaign, to get to the bank person who caused the damage. When you find out who this person is, contact the person in his/her "human being" capacity, rather than the corporate banking capacity, explaining the damage done, and gently demanding a reversal of the damages. Similar can be done with the credit bureau, but do the bank first if there is a way. If you can't find the person (because they cover for him/her), then go after the top person who covers, often the CFO.
If the banker makes it all good to your satisfaction, fine. If he/she doesn't, start a person to person - man to man, human to human - law suit the Karl Lentz way to break the corporate veil, and to bypass corporate attorneys. You will need to study to determine what to do. Or contact Karl in person.
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