I received just this same thing... my callerid showed a missed call from 50622048020 with no dashes (but notice there is one extra digit- I assume it is the zero at the end).  I cna't report it to the do-not-call site becasue it keeps telling me that it is not a good area code.

I received a call from this number on December 17th, 2008 @ 7:04 p.m. Central Time.  I wasn't able to get the phone, so it went to my voice mail.  No message was left.The number also had a 0 on the end.

I received a call from this number on December 17th, 2008 @ 7:04 p.m. Central Time.  I wasn't able to get the phone, so it went to my voice mail.  No message was left.

The number also had a 0 on the end.