If you are paying for both Premium and a Family Plan, one of these is usually the reason.
You joined someone's Family Plan as a member but kept your own subscription
Joining a Family Plan does not cancel your own Premium subscription. You have to cancel it yourself. Read How to cancel my subscription.
You subscribed through Apple or Google and did not cancel there
We cannot cancel an Apple or Google subscription for you. If you confirmed that you had cancelled but did not finish it, they keep charging you. Open your subscription settings on Apple or Google and cancel it.
You switched to the Family Plan on our website
This should not happen. We cancel your old website subscription automatically once the Family Plan payment succeeds. If you were charged anyway, message us with your account email and we will look into it.
Requesting a refund