They lie

I have the 1GB/s line and the top speed I get is 40pmb/s. They even sent people out to come and check what's going on and when they came still the same. I'm considering canceling with them. Why give a router that don't support 1gb/s. I had to go buy a router that can handle that speed but if I do a speed test on my phone that's 5g and my PC that has a bandwidth of 2gb/s I still get 400 mb/s