Hello, Nathan.
I see that the charge was against an automatic renewal of AVG TuneUp - Unlimited (30 day trial). When you subscribed for the 30 day trial version, you accepted for the auto renewal of this subscription for 1 year at the end of the trial period. You will be presented with this information while subscribing to 30 day free trial. We have also sent you a notification email regarding the auto renewal on 10th March 2018. Please check your inbox and spam box as well.
Anyway, I have forwarded your refund request to concern team. They will process it and get back to you via email with a confirmation.