The only person at LNER worth writing to that I know of is Mike Ross.
I had a dispute that was very long running in which I was not only incorrectly charged by a Guard but was mistreated by Customer Relations.
I eventually got a refund plus complimentary first class travel for any journey on LNER, but I had to fight for it. And, even more importantly, an acceptance I was right all along and LNER's internal notes were amended to reflect the correct contractual position.
I don't trust Customer Relations one bit as a result; they were well and truly incompetent. The story is far too long for here.