Hi @ashep665 . If you have FTTB or FTTN connection, you can use a longer telephone cable from wall socket to router to move router to a better position. If another type, you can use a longer ethernet cable from NBN box to router to move it to a better position.
If the router has to stay put, you can use a wifi extender. One type plugs into a power point partway between router and office to extend the router's wifi. Another type plugs into a power point and uses the house wiring to extend the wifi signal (both ends need to be on same electrical circuit).
There is also mesh types. The router unit replaces current router and works with a satellite unit.
If you use the VOIP phone service, you have to keep the TPG router as your main unit.
Easy Steps to Improve Wi-Fi Connection In Your Home
https://community.tpg.com.au/t5/Featured-Articles/Easy-Steps-to-Improve-Wi-Fi-Connection-In-Your-Hom...
https://community.tpg.com.au/t5/Modems-and-Devices/Wireless-Channel-on-your-modem-what-is-it-and-why...
