Companies can get a bit touchy about such things, not least of all because they bear some responsibility for things done on it. In the US I would not be surprised in the least to see someone fired for this sort of thing, don't know about Canada's work regs but "like a tonne of bricks" is not something I would be surprised about.
Anyway the answer depends upon the security they are using for it. For no security it is easy, for noted mac addresses then you will need to find a way to spoof that, for WEP it is pretty easy but you might need a certain class of wireless card to do it, if it uses WPS then there are ways around that (a few bad flaws were found it in a few years back, see something like pixie dust). Everything else (WPA and up) gets more tricky, there are also types of security that some higher end networks, such as those found in workplaces, use and you will likely never have encountered them outside of a big boy network.
https://www.aircrack-ng.org/doku.php?id=tutorial is a start for such things, the aircrack suite will likely be a part of any security Linux distribution like Kali that you care to find.
If you have access to a machine with a key already in it then you might be able to read the key back out from it
http://www.nirsoft.net/utils/wireless_key.html
Does the router have the password written on it? Or another one written somewhere.
Does it still have the router config password written on it? Most wired security is not there, connect via LAN and then read the password off from the config pages if that is an option.
Is it given out to guests? I have seen this in the past.
You can go one further and spoof the access point, possibly after taking the existing one offline, and then when something tries to sign in it says are you workwifinetwork and here is the password I have for, there are networks with various types of additional authentication though.
https://www.alltechbuzz.net/hack-wi-fi-password/ has a bit more.
Equally there are ways for older security types (see Cafe Latte attack) to do similar things.
Again for work I would not do this, too much aggravation and not enough gain. If mobile data is too expensive then kick it old school and download videos to watch, use lower bandwidth applications (an active text chat for a month is probably less than a coffee break watching youtube).
