Paid for 1 year subscription. Still getting advertisements. Nothing changed.
Have you gone through your options in the Help Center? They have a section for troubleshooting Duolingo Plus in there. To find it without the above link, hover over your username in the blue bar at the top of the screen (desktop version). A menu will drop down. From the menu, select "Help".
If you want a refund, but have gotten stuck in a loop of auto replies, please make sure you've submitted your ticket as a purchase issue via the bug report form. If you submit it as a bug or other issue, the sales department won't see the ticket. The bug report button is located at the very bottom of the Help Center page.