NCD Lowered at Renewal (no claims made)

Renewal time approaching for both my cars and I got a renewal offer on one of my policies but not the other (both with same insurer and both exact same dates). Interesting thing is I have 2 lots of NCD and on the one I got renewal offer for I should have 13 years and I paid for protected NCD etc. Now I know most insurers only recognize 5/7/9+ years etc for the purpose of the level of discount applied, but my renewal said 9 years not 13. I call and ask and am told they only do up to '10', I said that's dead on, so why's it not 10 then? I asked how when I go to another insurer do I show them my what should be 13 years? I have effectively having paid for protected NCD lost between the two policies 6 years hard earned NCD??? They said yes, but just tell them it was us and you really have 13 they will prob heard of this with us before.... I asked can they not simply give me a letter for proof of NCD with the actual number and they said no, words were exchanged and eventually I got said letter, but why not if you have the ability to do so give me one in the first place?? 

Thought it a bit strange as in the past insurers always stated my actual NCD accumulated regardless of the cut off point at which their own maximum discount is given. 

Good news with this years renewal, I got a higher price than last year, but they agreed to beat another quote I got making it cheaper. Best bit was the quote they beat was a price including cashback which would have taken 8 months to get in this case.

Bad news is the underwriter hasn't initiated my renewal for other car yet (same underwriter as first one LOL), so they can't even talk to me about it yet with regard to matching prices etc :(