@RealJoshue108 Discussed in RQTF - the we need more information about the user need for specifically identifying the relay call. Modality can vary depending on the user needs - you may need to direct or forward the call. What information needs to be directed. Is it origin, author etc?

NEEDSINFO - @joshueoconnor to go back to ITU-T

Discussed in RQTF https://www.w3.org/2021/01/13-rqtf-minutes.html

Reply from ITU-T: The request/ suggestion from me is based on the way text relay service is set up in UK. To receive a relay call, using an app on mobile the user needs to toggle between the app and the handset. If the incoming call is relay call, [the] user will immediately activate an app, otherwise the call maybe lost as quite often deaf people will not answer unknown calls. The party calling [the] deaf user [use's a] prefix to connect to [the] relay center. If the calling party does not use prefix for relay call, then the call with not have text relay assistance.

In [the] US, with captioned phones the situation is different as users have access to captioning "on the go", [the] calling party does not need to use [a] prefix and [the] user simply presses "captions" button to access text relay call as they answer.

@RealJoshue108 notes that this use of prefixes outside the US for relay calls may well point to the requirement. The user need is clearer based on this input from ITU-T