I'm sorry this has happened!!!
You have to be really careful. The late payment could have been on another credit card or a rent or anything that had been reported to the Credit reporting agencies. Bank of America jumped on it and charged the extra interest. I have seen BoA do that several times. Personally, DH and I would never choose to use BofA again, too many issues with us and with family members getting raked over the coals over the most minor of issues!!
We had a credit card issue with them. We had a payment due on a date that was a Sunday. Dh paid it electronically on Thursday, before the due date. They claimed it was late because it had to be paid by noon on Thursday to be counted for Friday because they don't accept payments on Sundays. It was paid before noon on Thursday, just when you make an electronic payment, they don't process them until the night. So, basically a payment was late unless you paid it at least 4 or 5 days early!!!