You may cancel your subscription here: https://www.chegg.com/tutors/change-subscription/.
Just choose the no subscription option, (Pay-as-you-go), to end weekly billing.
If you meant to cancel before this most recent subscription charge went through, we're able to convert your pre-paid minutes to pay-as-you-go minutes on Chegg Tutors. That way, the minutes you've paid for will remain on your account indefinitely. They won't be removed at the end of your week or month. You'll have the minutes on your account until you use them towards tutoring, or to pay for a new subscription anytime in the future.
To request this, please use the submit a request feature in the top right corner of this page (you'll want to choose "Rollover Request" as your request type, and simply indicate that you've canceled and want these minutes converted to pay-as-you-go).