Abrreviated to TPO, The Pensions Ombudsman is the UK’s independent organisation set up by law to deal with pension complaints.
They look at the facts without taking sides, free to the scheme member.
They will expect that you’ve already gone through the complaints process, known as the Internal Dispute Resolution Process (IDRP) and not agreed with the Scheme Administrator (Stage 1) and Dispute Handler (Stage 2) but may be able to provide support before then.