Someone called three times in 30 minutes from this number and before I could answer it, they hung up. When I return the call to this number, the line is always busy.

I received a call from this number.
At first, it is an automated voice asking to press 1 to see if I qualify for a reduced interest rate for credit card.
I pressed 1.
A man gets on the phone telling me that he works for Card Services and that Card Services is on page 2 of my credit card statement.  I quickly looked on my statement and see FIA Card Services.
I asked him what does FIA stand for and then he hangs up on me.

Received TEN calls in less than a minute when I kept declining the calls to my Cell Phone.  No voice mail left.  I have now added them to my Blocked Caller List.

Received many calls from this number, last one within the last 5 mins, a quick Google search indicates that it may be connected to scammers.

They called me too. Only once but I added them to the reject list with Kaspersky security app.