Just as info:
The standard trial is 7 days, not 30 days.
Simply said :
The "extended" (30 day) trial means you took a subscription of which the first 30 days are free of charge.
You should have disabled the auto-renewal in time.
You should count in business day, not weekdays.
Nevertheless 10 days (= 8 workdays) is not normal for avast to not respond to a ticket.
Did you check your spam folder for a mail from avast ?