In all the years that I have used avast I have never found a need to contact them.
There is an avast forum on this site.
I suppose avast has their own forum which you can post in.
Please be cautious about using Avast support. I could never be sure whether I had a legitimate support person or a fake group trying to sell fake services. I called more than 1 support number which I found on their website. I received the same shoddy treatment from each one, resulting in a loss of $100 for software I didn't receive. They claimed it was a 3rd party selling it to me. I will no longer use their product.