It is becoming confusing (at least to me) exactly what your issue is.
Your WiFi speeds will be dependent on the capabilities of the WiFi hardware on the phone (or other WiFi device). As others indicated you likely will never see close to 1GB WiFi speed unless you have WiFi 6 (160GHz) capable WiFi hardware on the phone or other mobile device and even then one may never see the full
marketing advertised WiFi speed.
Your first step should be to test a computer directly connected to the broadband provider's equipment using
Ethernet cable (do not use WiFi). Test the broadband speed with the Asus router out of the mix with only the computer directly connected to the broadband modem or gateway. Verify that the Ethernet connected computer is reporting the speed you are paying for with the Asus router not connected. If you are not getting the speed you are paying for, contact your broadband provider support line and have them check the line to ensure it was properly upgraded from 500MB to 1GB. Mistakes do happen and sometimes the line is not properly provisioned.
Note that broadband companies typically do not, on consumer lines, guarantee you'll receive their advertised maximum speed. They all use fine print language like "speeds up to 1GB" which means you could see 1GB speed or you could see 200MB speed. Further one's broadband speed can be affected if the broadband provider over provisioned the line and your neighbors or family members are all using that line at the same time (like evenings or after school hours).
Next, connect the Asus router to the broadband provider's equipment. And use a Ethernet wired connected computer to test the broadband speed. Do not test using WiFi at this point. Verify using a Ethernet wired computer with a Gigabit capable Ethernet port. If the broadband speed test verifies that you are receiving close to 940Mbps then you are receiving the speeds you are paying for (assuming 1GB plan speed).
Only then should you move to looking at the WiFi speed. Check the WiFi specifications for your WiFI devices. It is possible your WiFi speed may be limited by the capabilities of the phone's or computer's WiFi hardware. If the client device WiFi hardware is WiFi 6 capable then ensure the router has DFS/160Ghz enabled in the WiFi settings. Typically WiFi tends to be slower (for many reasons) than wired Gigabit Ethernet. Check and post the
System Log > Wireless Log page on the router. See what the router indicates for the WiFi device's connection. For example, if it indicates the WiFi connected phone has RX/TX connection of 300/300 Mbps, then the phone will typically be confined or limited to that 300 Mbps speed (or what ever speed the router indicates the device is connected at).
So post a screen shot of that Wireless Log page for others to see what you are seeing for what is being reported by the router for WiFi connected devices. Redact sensitive information if needed.