Is it an acceptable practice for banks to charge an overdraft fee on their own monthly fees, especially when those fees vary? More importantly, is it legal for a bank to charge an overdraft fee on their own overdraft charge? It results in two overdraft fee charges on the same transaction.

Legal - maybe, you would have to research your state laws to see if they address the assessment of overdraft fees. Conscionable - probably not. The first stop is your depositor's agreement, the second stop is the bank president's office, the third stop is your attorney's office.

The bank is BB&T. Do I research the law in their HQ home state, the branch where I opened the account (DC) or where I live now?

You should look at your depositor's contract to see what rule of law you contracted to use. You might need an attorney to determine their ability to export laws over the State line or supersede your State laws. It's sometimes a complex issue under you are dealing with a federally chartered institution.

You might start by calling the branch you opened the account at. There may have been a computer glitch that they didn't know about. Call and see what they say before you spend all day researching something you may not even need.