A Washington-based nonprofit is behind the "Lamont Williams" calls.
The nonprofit told the Institute for Southern Studies, which runs the Facing South blog, that the calls were part of a 24-state effort to register unmarried women. But the calls do not mention the group's name, they come from an unlisted number and they are misleading.
The calls tell voters to look for a voter-registration packet in the mail, but they were made after the deadline passed in North Carolina for mail-in registration.
Complaints have been made in Wisconsin, Michigan and Arizona about similarly misleading calls.
"The reports from other states are very disturbing, especially the pattern of mass confusion among targeted voters on the eve of a state's primary," Democracy North Carolina's Bob Hall told Facing South.