Nothing is untraceable to the feds.......
The VPN provider would be served with a warrant and they would provide the originating IP and MAC they masked.....Even bouncing off several VPNs would only slow them down maybe 24 hours...
WE 1011B,(or similar device) find a telephone Distribution Point , connect to a working number and dial away!
Then pray that the line you used, belongs to a LIBERAL!
FJ&JB