47 CFR §64.1508

1. (a)Local exchange carriers must offer to their subscribers, where technically feasible, an option to block access to services offered on the 900 service access code. Blocking is to be offered at no charge, on a one-time basis, to:
   1. (1)[Reserved]
   2. (2)Any subscriber who subscribes to a new telephone number for a period of 60 days after the new number is effective.
2. (b)For blocking requests not within the one-time option or outside the time frames specified in paragraph (a) of this section, and for unblocking requests, local exchange carriers may charge a reasonable one-time fee. Requests by subscribers to remove 900 services blocking must be in writing.
3. (c)The terms and conditions under which subscribers may obtain 900 services blocking are to be included in tariffs filed with this Commission.