Paragraph 25.8
Customers who need to use Textphones because of their disabilities shall be charged for the conveyance of such voice and text messages to which a Relay Service applies:
at no more than the Licensee’s prevailing standard prices or such other charges as are, so far as reasonably practicable, equivalent to such prices as if that conveyance had been made directly between the caller’s Network Termination Point and the Network Termination Point of the called person, except that the calling customer may be charged at the Licensee’s standard local call prices for the element of the Relay Service which consists of calls made to the Relay Service provider in order to make a call to a called person irrespective of whether the call to the called person is successful; and
by the application of a special tariff scheme designed to compensate customers who need to use Textphones because of their disabilities, for the additional time taken to make telephone calls using a Relay Service.