47 C.F.R. § 64.1505 – Restrictions on collect telephone calls.

(a) No common carrier shall provide interstate transmission or billing and collection services to an entity offering any service within the scope of § 64.1501(a)(1) that is billed to a subscriber on a collect basis at a per-call or per-time-interval charge that is greater than, or in addition to, the charge for transmission of the call.
(b) No common carrier shall provide interstate transmission services for any collect information services billed to a subscriber at a tariffed rate unless the called party has taken affirmative action clearly indicating that it accepts the charges for the collect service.