If it's a wet clutch DSG where the transmission fluid is shared with the clutch pack, change the fluid and filter every 3-4 years. It's actually a reasonably straightforward job that can be DIY. Confusion arises because the dry clutch lightweight low torque 7-speed DSG in which the fluid is not shared with the clutch was originally filled with synthetic long-life fluid, but it was later discovered that this becomes conductive at high temperatures leading to loss of drive, so there was a worldwide TSB (not a safety recall) to replace this fluid in affected cars up to about 2012. After this has been done, Volkswagen says no need to change the fluid again. But independents say it needs to be done every 4 years.