For achieving this, you need to buy a phone and SIM card with cash and without is card. Then you should not install banking or govt or any apps that can expose your real identity. I can make the list very long, so before getting worried of being tracked just using your signal number for the registration, there are many issues to consider. Lastly, you cannot be tracked down because your signal number but because your operator shares your location. In that case, you can buy another card after activation or use it with WiFi.