No, you can't just cancel any service by blocking your card payments. Legally they are quite distinct actions, and depending on the situation, you may find yourself with debt collectors chasing you quite rightly for money you legally owe, damaged credit, etc.
If the service provides a reasonable means of cancelling, just use it. If it doesn't, take other action as appropriate, but don't just silently block payments without making a reasonable attempt to tell the service you are cancelling.
He sent an email, he has a response denying the request. Why would that not be enough? The company here is at fault for outright refusing a written request.
Email isn't secure. It's unreasonable to expect that to be sufficient to cancel anything with consequences on its own. I agree that the company is in the wrong here, but not because they wouldn't take significant and possibly irreversible action based on just an email that could have come from anyone.
"Email isn't secure, that's why you must make a phone call because the only way we can verify it's actually you is by hearing your voice, which we've never heard before"
No, you can't just cancel any service by blocking your card payments. Legally they are quite distinct actions, and depending on the situation, you may find yourself with debt collectors chasing you quite rightly for money you legally owe, damaged credit, etc.
If the service provides a reasonable means of cancelling, just use it. If it doesn't, take other action as appropriate, but don't just silently block payments without making a reasonable attempt to tell the service you are cancelling.
</response>