Bank charges fees on emptied and abandoned accounts - Texas

We had several low activity business, personal, and custodial accounts at a local bank. The bank was bought out by a national bank. We decided to consolidate our accounts at our normal bank instead of this local one. We went to the bank and emptied the accounts. I intentionally did not close at least the business account at that time because I needed to download the history first. We started receiving bank fee charge notices in the mail for the accounts that the balances were below the minimum. I called the bank twice to report that none of our accounts are active and they should cease sending the notices and close the accounts. They told me that we would have to go to the bank personally to do it. I notified them that we would not waste the time to do that and they should not waste their admin fees by sending us any more notices. We would no longer even take the time to open the mail from them up. The customer service rep said they could not close the account nor stop the notices from her system. Today, I got a notice from a collection agency that the bank has turned the matter over to. It is for $54. What are my options? I do not intend to waste time or pay the bill. Can I sue in small claims court for damaging my credit history if they create an issue? Should I contact the collection agency at all?