scam

I called Xfinity to cancel my cable and just get internet access.  I was informed that I needed to pay my current bill, I informed them that it is automatically taken automatic; they informed me that it expires at the beginning  of the year and to give them my credit card and accept a code.  When I went to return the box to the office the next dat I found out It was a scam.  I was told that xfinity does not request payment over the phone.  I cancelled my card but I'm worried my account has been compromised.