Spoof call from Comcast

Just got a call from the Xfinity Number - 1-800-266-2278. Guy with an indian accent, calling me from a loud call center. Said something about my firewall being compromised. Asked me to go to the modem - he said he would send a signal to it.  I told him I don't see any blinking lights on the modem. He then asked me to go my PC and go to this website. I said I don't trust you, I'm calling Xfinity back. He said I am with Xfinity, I can provide your name and account number. I didn't relent and he swore and hung up on me. How is Xfinity allowing these spoof calls to happen?