I'm surprised to hear people say that it's Credit One. I've had my card with them for about a year with no problem. Are you sure it's not some scam/hacked situation with people posing as Credit One? I got 8 calls today (Sunday) and 4 yesterday. My ID just said "Maryland."
It's for sure Credit One. They will disguise the numbers with Duffy area codes. I know it's them because I called them back , big mistake! And got into it with some guy who proceeded to lecture me on responsibility!!
It is credit one bank. They call from a variety of numbers, I answered the call because it was from my area code and a city where I have some elderly relatives. When I finally got someone and they said it was credit one bank, I asked them if they knew where the city was and they couldn't tell me.