Try all of the above to unsub yourself first, but if you do and it doesn't work, then contact the List Administrator and ask to be removed from the list. You may have been subscribed twice to the list. But when you unsubbed, only one address was removed, leaving one still on the list and hence you are still subbed. Please check with the List Administrator. Your mail could have been bouncing without your knowing it.
Most lists limit the number of bounces an address can cause before it is automatically unsubbed.
This may be as few as three. On a busy list, these bounces could reach the limit in a hour, others may take days. It is posts TO you, not FROM you, which are causing these bounces. This happens when your mailbox is full, or when your ISP is offline temporarily. You would normally receive an unsub notice, but if your email was bouncing, this notice may have bounced too.