The Justice Department is accusing AT&T of improperly billing a federal subsidy fund for calls made by Nigerian scam artists, in a lawsuit announced today. AT&T allegedly sought reimbursement from the Telecommunications Relay Services Fund for calls it knew were not eligible for the subsidy, particularly from foreign callers who sought to defraud U.S. merchants, according to the Justice Department. The fund is administered by the FCC for “IP Relay” calls, in which hearing-impaired people make telephone calls to hearing people via Internet messages that are facilitated by IP Relay providers.