Yes you can..just put it on bridge mode

Ok this is so simple.
first off the router has ethernet,
and you can run 10 Access points or more in home..
off that 1 port. (router to AP1, then to AP2, and to AP3
all wired, then each with its own SSID. that is how I do it
and gains max range doing so.
if you like magic, get a MESH AP. (but is expensive)

and point 2, all AP even modem wifi or router wifi can be turned off easy, the manual is free to read, and the box to check is called

disable. wifi. for sure.

if you cant tune off wifi in the ISP modem and they will not help you then just leave it alone, ignore it
and setup an AP with its own SSID.
even use different channels, too. for sure.