Welcome to the Community @flora711
Before attempting the troubleshooting steps, TPG recommends that you to check our Service status page if your service is affected by an outage.
If your service is not affected by an outage, then we've created an article that will help you on how to troubleshot slow speed issue.
In your case, we've raised this with our Engineering team for further investigation and decide if a TPG or a Telstra technician is required to fix the fault. An assigned Engineer will be in touch with you via SMS or phone call once available.