He probably contacted Comcast and some time during the call(s) he played the "I'm a lawyer" card and maybe hinted at legal action. At this point, the customer service representative would be required to turn over the call logs to internal legal counsel. Comcast's counselors did their homework and figured out who this individual was and then contacted his firm to discuss the threat of litigation. His firm was probably like, "WTF?" and canned him because they would rather their employees didn't go around trying to intimidate others and/or get preferential treatment just because they have a law degree.
Again, playing devil's advocate here.