I think a better approach is to just require business to accept certain standard ways of being informed of cancellation. I.e. they must accept an email, a phone

I think a better approach is to just require business to accept certain standard ways of being informed of cancellation. I.e. they must accept an email, a phone call, a letter, etc. If they then want to have an even simpler cancellation flow, that is fine, but they must accept all of these basic methods. This is how it works in Sweden.