I received 2 calls from the same number.  The first time they did not leave a message.  The second call I answered, it was Comcast Cable repair department.

I received a call from this number at 3 a.m. Woke me up! Why are people so inconsiderate? I looked at number know nobody from there, so didn't answer and went back to sleep!

Just received 9 phone calls in 7 minutes from this number. No messages but when I called back got a recording that the number was not in service.

I was troubleshooting some phone issues with Comcast.  The phone rang with this number and when I picked it up, the person hung up.  I got another call a few minutes later from the Comcast 800 number, and they said they were doing a test call on the phone - and 904-486-3950 is the number they used to do the test.

I received a call from this number as well...they identified themselves as a Comcast supervisor following up.  They asked for my 'password' to 'unlock' my account so that they could see what was going on.  I told them 'well you have my account open because you called me'.   This question was answered with a 'well I need your password to unlock it?'   I said I'm not giving it.  You're a supervisor -- you have this information -- you need nothing from me because YOU ARE CALLING ME?   They would not let up in this -- so I said that if you think I'm that stupid -- I know this is a scam and you're done!  

I hung up.  Never got a call back.
Talked to Comcast the next day.  They do not have 'supervisors' calling customers at night.  He took the number and was sending to fraud and securities because that was NOT how Comcast handles this process.

Just be very careful even if they tell you they are comcast.