Random Call about my Modem

I got a recent call from someone claiming to be from Comcast. The ID says Xfinity Store by Comcast 1-800-266-2278. He said there was unauthorized activity on my system and to check my router for flashing or blinking lights. He seemed to know who I was and it sounded like a busy call center and the line was extremely static filled and hard to hear. I eventually hung up cause it seemed suspicious. (I should have played with him a little bit more.)