I know I'm late to the game, but for future users who find this thread, this feels like a good use for TRANSLATE().

SELECT TRANSLATE(column, "AF", "BZ") FROM table

This has the benefit (or curse) of catching any variation. "Column A" becomes "Column B" for instance. It also means that "Alvin" becomes "Blvin" - which may not be intended behavior. Check your db, table, and column settings to see what consideration you need to give to case sensitivity.