Your problem is not the phone.

Rather, your problem is the WiFi router.

You need to get one that supports at least 1900mhz frequency on the AC spec.

https://www.amazon.com/TP-Link-Wireless-...

The AC standard will let you run as fast as your Fiber connection is, with perhaps a 10-20% speed degradation due to environment.

Also, the speed metrics may be a bit deceiving.

Speed on the Internet service is measured in Mb/s.

Download speed on a Browser is measured in MB/s (note b vs B).

There are 8 bits (b) in a Byte (B).

So you will have to calculate speed by dividing 250 million bits by 8 and possibly deducting another 10-25% (environment) to get the speed you theoretically should be getting.

So theoretically, you should be getting 27-31MegaBytes per second download speed.