They can turn off the wifi and you can use an access point.
Great ones like unifi ap lite run $80.
You can find an AC ap or router under $50 that will work.
You could also look into replacing the modem/router with your own. You won't pay any of those fees but they also won't help troubleshoot many issues with you. They might not allow you to replace the modem and you need to know if it's compatible. They can't force wifi on you.