I had a missed call from this number and i called it back and it was for discover bank. so i looked up the website for discover bank and i could sign in to my discover card account from there so yes it is legit.
I received a call from 302-323-5500 today, looked the number up, it said New Castle, DE "unknown." Called the number back using a different phone, when they answered the first thing she asked for was my account number; she said that it was Discover, yeah right. When I asked about this number they claimed that it was showing up on their caller ID as my number! I asked if it was a legit number, was told that it was a branch bank and probably a marketing call, go figure.
Beware, I didn’t trust the number.
I did call both 800 numbers for Discover bank and Discover card and was assured that in fact it was a legit number so I asked to opt out receiving marketing phone calls.
This is a perfectly legitimate call, it's from Discover, in fact it's likely they are trying to call you with something important about your account. Don't say it's a scam when it isn't, do your research first.