All good.”
No, not all good. There’s the problem right there. If I stop paying you can stop providing me the service I’m paying for. Using WiFi has nothing to do with you. Breaking my property this way, without a court judgement allowing you to do it, is not only unethical, but should be a criminal offense, and is at least a civil tort.
The potential liability here is literally unlimited. I believe responsible cell providers allow you to call 911, or the equivalent in your location, even if your account is delinquent. But you can’t do that if your phone is locked in this way. Did anyone die because of this product and this guy’s recklessness?