Report phone scam

Received a call from Xfinity Billing Dept with 50% discount for two years as long as I pay first 6 months up front for $990 with prepaid Target Card.  Actually looked legit because they knew my balance due for April and removed it from my account temporarily where balance due was $0.  Provided Billing phone number [Edited: "Possible Scam Phone Number"] and authorization code# [Edited: "Personal Information"]. Also sent email with info.  Too good to be true and why a Target CC or PC....hung up and my normally monthly billing reappeared on my account.  Changed my password.