Ring UK ombusdman

In the absence of any clear cut form of communication in writing with ring, I lodge a complaint via phone about their agents, which doesn’t get actioned - why would an agent refer themselves if they’re subject to a complaint [\sarcasm] I don’t believe they provide a service I pay in for, in this instance and have exhausted every means possible to lodge a complaint; so now the only available option is an external party What ombudsman would I contact?