WAN capped at 100mb help please! asus 87u

hello everyone.

i have an asus 87u a problem that my ips just upgraded me from 100 mb to 400mb download.

but im not getting my full speed. when i go to speedtest.com it shows i got 100mb when i should get 400mb

i already change my cable to a cat 7.
i rebooted the router.

is there any fix for this?. i read some posts that it could be auto thing

thanks for your help