To stop paying your council tax, simply cancel your direct debit, don't enter into anything with them until they send you a reminder, then once you have a reminder send them the following letter. Do not phone always by letter or email so you have a paper trail of everything that is said.
If you are worried, you can always put the money aside, even if you just stop paying for a few months it is something.
17th April 2021
Council Tax Reference Number
Dear
Thank you for your letter dated . We are willing to pay any alleged lawful debt regarding to this letter providing you can produce the following:
1. Proof that the debt exists.
2. A signed contract between ourselves stating that I am willing to pay for Council Tax
3. A signed consent form from 67m people in the UK to say they agree to the act being lawful.
Once I have received all of the above I will happily pay any outstanding alleged debt. The only correspondence I require from you will contain all of the above.
Any further correspondence from yourselves regarding this matter which does not contain the all items above, will be charged at a rate of £250 per document. Any visits to my premises will be charged at a rate of £5,000 per visit. This is non negotiable. Your acceptance of this letter is deemed your contract.
Without prejudice
Yours sincerely