For apache, I would just say disable the virtualHost which listens at port 45080. I’m not sure if you can directly access the config files or if you need to go through a special configuration tool. So it’s rather a qnap-specific question…
If Apache2 behaves as it would normally do, disabling a vhost config should be as simple as a2dissite xxx.conf where xxx would often be 000-default on servers. This would need to be done over SSH if the option in the web interface doesn’t exist.