First posting your email address on a public forum could get it harvested, not something you would want. I suggest that you remove it using the modify button.
Use the - Sales change order details wrong email address given, etc. - Submit a support ticket
https://support.avast.com/en-ww/contact/sales in your case select the Billing, payment, or license issues option - and then the I have a different billing or license issue and click Next and follow.
Here you can explain the problem, give as much detail as possible to help them find your purchase/order. You will almost certainly be asked to provide an Order ID, but you are unlikely to have that since you wouldn't have got an email. Enter 0000000 as your order ID that should get you past that hurdle and at least be able to explain the problem.