FYI here is the 2nd amazon reply
"After reviewing our previous correspondence with you, please accept my apologies for any misunderstanding caused.
This situation was the result of a combination of technical and human errors, and I'm sorry for any inconvenience caused.
Please allow me to try to provide a resolution for you.
I understand your concern regards received a Kindle unlimited free trial notification on your Kindle Fire.
I've checked your records and see you've activated the free trial of Kindle unlimited long time ago and you're eligible for another 30-days free trial Kindle unlimited.
In this case, we suggest you to sign up for the free trail using the following link: https://www.amazon.co.uk/kindleunlimited
However, if you get charged for activate the free trial, please reply back so that we'll issue refund to use the subscription as free for 30 days.
Should you require any additional information or assistance, please do not hesitate to contact us.
"
but I may pass - now that I can anyway get prime reading fro free, I'd struggle to find stuff to use it for. I can borrow better fiction from the public lending library if I plan ahead and place holds on the most popular stuff, and its not easy to sort only KU for specific non fiction subjects. e.g. my failed attempt to search the UK site search for KU books on "bitcoin" , which i mentioned in another thread