5g home internet - phone not autoconnecting..

I found a workaround, which was to use a wifi range extender I had around. I use the range extender to connect to the Tmobile gateway, then connect my phone to the network provided by the range extender.  I can now turn my phone wifi on and off and it'll automatically reconnect to the range extender network. Which so far has remained connected to the gateway. I'm using a TP link RE200. On my phone, the download speed is half what it is on my desktop which is connected (wirelessly) directly to the Tmobile gateway. Since I don't do a lot of heavy activity with my phone I think this should be OK.