Are you sure you can’t with Paypal ?
https://www.paypal.com/us/selfhelp/article/FAQ1916/8
https://www.paypal.com/us/selfhelp/article/i’ve-signed-up-and-paid-for-a-preapproved-payment-agreement,-such-as-a-recurring-payment,-subscription,-automatic-billing-or-installment-plan.-how-can-i-find-it-faq1916
nb:sorry , I’m in France and links are showned in “fr”(DNS) undeed “us”
even if it was not for avast, I was able to delete an automatic renewal of another site by this way in my Paypal account

however, I completely agree, the technical support (and especially commercial) is far from what it should offer for a commercial company, with sales passing through third parts and the difficulties avast has in gathering essential information.
There are enough reports here to show that. :wink: :-[