It may be more because people havent got enough data on you, rather than someone having to much (after all, they got it wrong didnt they). It seems more likely they are infering things about you from the small amount of info you have. After all, if I was to send someone something in another uni, and I didnt know if they were a doctor, I would call them doctor regardless. It would be more about trying not to offend anyone.
After all, you prob said on your application im doing a PhD. Your credit company may think that this is like a normal degree and you are more or less guarenteed the doctorate. So instead of giving you a card you have to replace in a year or so, they are giving you one in anticipation that can have a long expiary date. This has prob then gone onto your credit record when that application was accepted.