You would need to raise a complaint with the Financial Ombudsmen Service and advertising standards. What you need to do is request the recorded phone call for when you took the multi-car policy out, and use that as your evidence. What I would do is when you try to obtain a new quote, use your Admiral policy details as the contact for proof of NCB. Your details are already on CUE, the underwriting database. Technically, you should not need to provide proof of No Claims as they already have proof and access to that information via CUE. You can contact the Motor Insurance Database (MID) and request all the information they have on each of you, and it should show your no claims history.