NEW DELHI—One of India’s largest telecommunications companies says it has been told by regulators to stop providing Facebook Inc.’s controversial free Internet service.

Reliance Communications Ltd.—the Indian telecommunications company Facebook collaborated with to provide its “Free Basics” program aimed at enticing more people onto the Internet with limited free access—said Wednesday that the Telecom Regulatory Authority of India had asked it to stop providing the service while weighs whether the service is legal.

India’s...