Comcast/Infinity charged for international calls that I never made Internet

I have been a Comcast Cable customer for over 7 years.  In April, I let one of their customer reps convince me to sign up for one of their bundle packages.  I was with AT&T for phone and internet services.  The rep provided what appeared to be a good deal for cable, phone and internet for less than I was paying so I signed up.  The service installer came to my home to install the modem/phone box for service on April 12th but was unable to start the phone service because my number wasn't ported to Comcast yet.  It was still with AT&T.  Comcast finially ported my number on April 22nd.  I received a bill in May for international calls to CUBA for almost $500.  The calls were only made on two days (April 13th and 14th.)  I have been going through this with Comcast for two months now.  They are not smart enough to see that I do not owe this bill.  Now they have disconnected my services due to non payment of this stupid bill.  I continue to fight it though, I refuse to pay and refuse to have this on my credit.  I have made a report to the FCC for this also.