How to raise a formal complaint?

I purchased a ring doorbell last year which was initially on the standard plan. I found it useful so decided to add a stick up cam for the rear garden. All appeared good so I upgraded the £XXXX plan to the protect plus plan at £XXXX. This is the only plan that shows in my account, yet every month they continue to take the £XXXX alongside the £XXXX. On the 23rd April XXXX I contacted ring through the online chat and they agreed that there was an error and refunded the overcharged amounts. That should have been the end of it but the very next day my stick up cam stopped recording video and wouldn’t access live view (what a coincidence!). It was detecting motion, health was good with good signal and everything was online apart from the video that kept asking me to reconnect. Except of course it won’t connect or reset. I’ve even tried deactivating the camera to set it up from scratch but I cannot get it to enter set up mode. Given that it was only a month or so old and clearly wasn’t fit for purpose when it was sold I tried contacting customer support for advice on how to return it for a replacement. Over 43 phone calls later I still haven’t managed to speak to anyone on any of the published numbers. The menu system gets to about the third option then crashes out with a ‘I didn’t get that’ message. To add insult to injury, I find out that they’ve taken two payments again in May and June. Absolutely useless! So here I am, paying a total of £XXXX a month for something that doesn’t work with no way of cancelling the £XXXX part of that through ring. Unless someone can actually provide me with an email address or postal address to raise a formal complaint then I don’t see any option but to raise immediate concerns with my bank over fraudulent and unauthorised deductions from my account and seek legal advice over the camera that is unfit for purpose.