47 CFR §64.1503

1. (a)Any common carrier assigning a telephone number to a provider of interstate pay-per-call service shall specify by contract or tariff that pay-per-call programs not in compliance with § 64.1502 shall be terminated following written notice to the information provider. The information provider shall be afforded a period of no less than seven and no more than 14 days during which a program may be brought into compliance. Programs not in compliance at the expiration of such period shall be terminated immediately.
2. (b)Any common carrier providing transmission or billing and collection services to a provider of interstate information service through any 800 telephone number, or other telephone number advertised or widely understood to be toll-free, shall promptly investigate any complaint that such service is not provided in accordance with § 64.1504 or § 64.1510(c), and, if the carrier reasonably determines that the complaint is valid, may terminate the provision of service to an information provider unless the provider supplies evidence of a written agreement that meets the requirements of this § 64.1504(c)(1).