Oil might work for a squeaky hinge, but if it's actually joining calls, that sounds like an electrical short. Could be a faulty sensor in the seat or a problem with the connection to your computer. Mine just creaks, but random button presses would drive me up the wall.
Watch a tiny sensor glitch and suddenly your chair's joining calls for you. Makes you wonder if tech waits for the worst possible moment to break down.
My old laptop used to randomly blast music during quiet moments, like it had a mind of its own! It turned out to be a stuck media key on the keyboard. Tech just finds the worst times to act up.