OK not a lot you can do then. If you can access the modem and get the model number and if they are stupid enough to leave the password at the factory defaults then you may be able to turn uPNP back on and solve this problem via the wifi but that is doubtful. If they have changed the password then you would have to find the reset button and reset this modem. Then you can lookup the default password at
http://www.setuprouter.com and attempt to proceed from there, but WARNING if this modem has a static IP make sure you know what the IP address, subnet mask and default gateway numbers are before you reset it as these will be lost and of course if you do not know the password you are not able to do this.
A way round that of course is to phone the ISP help line and ask them for the static IP address after the reset but they will ask for the account details, but as this is student accommodation that could get you into trouble
It is up to you how big a risk you wish to take, resetting the modem would of course be a way forward if the IP address is not static, if it is then as long as no one sees you doing the reset, you are fine. The internet will then be off for everyone until an engineer is called from the service provider to poke that info back in again. He or she may then be approached to see if they will leave uPNP turned on for you all.
Again that can be done remotely so you will not even see the engineer so you may well be stuck.