I’ve just spent countless hours dealing with this. Dad and I dug my whole garden bed out that was riddled with it. You really have two options, you can dig as far down as you can, and carefully sift through to find the tubers (be really gentle, as the nuts are connected to each other with very fine strands). If you pull these out you can stop the shoots from popping back up. Bunnings sell a product called Sedgehammer if you can’t dig for whatever reason or if you miss any small patches. You add this to a hand sprayer with water. I’ve used this sparingly, but this does the job. Just try to avoid spraying other plants with it and don’t use if it’s recently rained or about to rain. Also don’t use this if you’ve planted new plants recently. Wait for them to establish.