We provide a modem/router depending on the stock availability. For wireless issues, we did an aritcle that you may find helpful.
This will guide you a basic step-by-step troubleshooting on how to improve the Wi-Fi connection please see the links below.
Wireless Channel on your modem - what is it and why should I change it? - TPG Community
Easy Steps to Improve Wi-Fi Connection In Your Home - TPG Community
Let us know how it will go.