Only agreed to pay monthly, charged full yearly amount

I wanted to subscribe to Ring Protect Basic for my Ring Video Doorbell v2. I clicked monthly, and the payment went through as full yearly price!! I didn't request that, and didn't authorise that amount. I was given no warning, and the only way I realised was when I checked my bank to make sure the payment went through! What's this all about? It asked if I wanted to pay monthly and I did, yet it took for a full year?