Hi
I can understand your frustration. I think it’s unfortunate that these kinds of pop ups cause people to believe there is a problem with an agenda to slick a user into an unnecessary purchase and residual issues that result. :-\
https://support.avast.com > Submit a Support Ticket, explain your issue in detail if you want support.
OR you can Request a Refund. 
You do not have to pay for support with a Ticket.