Just had one of these happen on Firefox, which locked the browser and required Task Manager to kill. The “Support Center” number was 1-833-724-2905. When I called it, got an autoattendant and then an agent with an Indian accent, so I think it is for real.
[[3],[3,4,27,37]]
Number appeared to go dead about 3 pm Central! Way to go, whomever pulled the plug.