47 CFR § 64.6050
Billing-related call blocking
February 16, 2021
No Provider shall prohibit or prevent completion of an interstate or international Collect Calling call or decline to establish or otherwise degrade interstate or international Collect Calling solely for the reason that it lacks a billing relationship with the called party's communications service provider, unless the Provider offers Debit Calling, Prepaid Calling, or Prepaid Collect Calling for interstate and international calls.
[85 FR 67462, Oct. 23, 2020]