The my(dot)avast(dot)com is completely separate from the billing department.
If nothing else you have the option of contacting you credit/debit card provider
and put a "stop" on the payment.
Dell Inspiron, Win7x64 SP1, Comodo Firewall 5.12 w/D+, MalwareBytes Free 2.1--HP Envy Win8.1x64, MalwareBytes Premium 2.1--Both systems Avast Free v2015.10.2,2218, Super Anti-Spyware, Spyware Blaster, MCShield, Unchecky, Firefox (latest build), Google Chrome (latest build) and, various browser security tools.
When you do something, do it with a purpose and do it on purpose.