Google finds that GSS is short for General Social Survey and that it’s one of the nation's longest running surveys of social, cultural and political indicators. See http://gss.norc.org/ The pattern of calls where they refuse to be informative when you call them fits in with opinion research or surveys.
"Steve Miller" of GSS is using 201-204-0022, 201-204-0023, 201-204-0024, 201-204-0025, 201-204-0026, 201-204-0027, 201-204-0028, and 201-204-0029.