Automatic renewal fee

I cancelled my subscription on March 13 and uninstalled Avast on my computer. However, I nevertheless received an email that said that my subscription was renewed and my credit card was charged on March 15. This charge should be cancelled immediately. I will not pay it. I don’t remember ever agreeing to automatic charges, and I suspect that the company is being unethical.
But I cannot find any way to talk to somebody at Avast about this problem. What should I do ?

https://www.avast.com/faq.php?article=AVKB24#artTitle (Orders and Renewals)

https://www.avast.com/faq.php?article=AVKB24#idt_0430