They called even though the payment wasn't due. Remember collectors have consumer protection laws they have to obey.Tell the rep they don't have permission to call you and they must stop. Once they see you are aware of your rights they will leave you alone. As for credit one itself absolutely pay off and cut that card.
Today they(credit one) have called me three times so far, starting at 830am. Today is Dec 19. My bill is due on Jan 13. Absolutely no reason to call me. Can't wait to pay this off.