Updates a ring group in place: your body is merged over the current group, then the group and its call routing are rewritten. Every key you send is applied, including an explicit null, so send only the fields you mean to change. Destinations follow the presence of ring_group_destinations — omit it to leave members untouched, send an array to replace the whole set, or send null to clear them all. The updated group is not returned, so re-read it with GET /api/v1/ring_groups/{id}. Identity fields are not settable here: the record's own id, its account, and its call-routing id are always taken from the stored record, and sending them has no effect.