In your AVG my account "products" page, Click the arrow button next to your product to expand the product description, and then click Cancel Subscription. Keep us informed about the status.
I have the same problem, using Firefox. I seem to have multiple subscriptions, such as Ultinmate Security plus SecureVPN plus AntiTrack. I want to get rid of the duplicates, but there are no options on the My Account page, nor any way to contact AVG.
In your AVG my account "products" page, Click the arrow button next to your product to expand the product description, and then click Cancel Subscription.
Keep us informed about the status.
Can you try it from a different browser and inform the status?