There was a recent increase in the plan. It should be mentioned in the last page of your previous bill in small print. You might see something like this: 

Update to your monthly rate plan. Update to your monthly rate plan. Starting in March 2022, your monthly rate plan fee will increase from $35 to $40. In accordance with the service terms, you accept the change by continuing to use the service. If you do not agree with this change, you may cancel your service without penalty within 30 days of the effective date of the change.

Login into self serve. Download your detailed pdf ebill. The notice for the price increase is noted in here. If you don't see it download the pdf ebill that is the previous month 

This is why we all should be carefully looking at our invoices every month.  That said, I’m as guilty as most people of not doing that regularly.

“In accordance with the service terms, you accept the change by continuing to use the service. If you do not agree with this change, you may cancel your service without penalty within 30 days of the effective date of the change.”

That seems suspiciously like a ‘negative billing option’ which I thought was outlawed in Canada.

I don’t think rate plan increase is similar to a ‘negative billing option’ . The regulation from CRTC is here https://crtc.gc.ca/eng/internet/codesimpl.htm

I guess maybe we can agree to disagree.

Not that laws are perfect or its correct, but it's currently legal. I personally don't like that it's placed at the end of a bill by Koodo. But it's still considered a notification.

Here is the regulation:

Notice of Changes      8 (1) An institution that makes any changes to the terms and conditions that apply in respect of an agreement for an optional product or service must, not less than 30 days before the day on which the changes take effect, disclose in writing to any person who subscribes to the product or service the changes to the information that was required to be disclosed in the initial disclosure statement.

https://laws-lois.justice.gc.ca/eng/regulations/sor-2012-23/page-1.html#h-784812