Duolingo Subscription Was Activated Without My Consent

My mobile phone line is on a postpaid plan, and I recently discovered that my June phone bill included an approximately $19 charge for Duolingo that was added without my knowledge or authorization. Neither I nor any member of my family purchased a Duolingo subscription.

As soon as I noticed the charge, I contacted my mobile carrier's customer service. I was told that a Duolingo subscription had been activated through my phone line, which is why the charge appeared on my bill. I immediately canceled the subscription, but I do not believe it is acceptable to be billed for a subscription that was activated without my approval.

I request a full refund of the approximately $19 charge that was added to my phone bill because of this unauthorized subscription. The charge is still reflected on my account, and I ask that this issue be resolved promptly. I also request that appropriate safeguards be put in place on my mobile line to prevent any similar unauthorized subscriptions from being activated in the future.