Do that - cancel your subscription.
When you do, you will probably be offered an incentive to stay. I was offered two months' free, and someone else was offered one month free.
I can't remember which came first - if I said 'no' to that, or if I scrolled down the page and saw an option to change my account to 'classic' (I think that's what it's called). Maybe I had to say 'no' to the offer before I saw the option to change my account.
Anyway, the 'classic' account is the same price as before the recent increase, and drops CoPilot and that annoying little thing on the side of Word documents.
Downside: you do have to wait until your current month expires (or possibly current year, if you have an annual sub) before it takes effect.
For me, that was the 28th. However, the change did not occur until 29th.
I no longer have CoPilot (which I never wanted) *and* the cost did not increase.
Not great customer service to have to jump through hoops to get rid of something you never wanted, though.