IPv6 Only Provisioning

My provisioning was changed from dual stack to IPv6 only with a recent upgrade in my neighborhood. Ever since, I have been having connection drops with certain Internet activity, mostly connectivity that requires a constant connection. I can't run a speedtest without error (speedtest.net). My research has shown that tunneling IPv4 packets over IPv6 is problematic for older sites. I want my provisioning set back to Dual Stack, but I can't seem to speak to a human from Comcast. How do I get a human comcast tech from the US on the phone?