If you have been attending classes in Concordia then you just can't run away or become absconding. You will need to follow the withdrawal process defined by the University. Approach the admissions department and they will guide you with the procedure. Withdrawing from program is not a crime. But, remember, you just can't run away in this case.
However, if you have not started attending classes then just decline the offer and leave the country.
If you have offer from some other institution then get your DLI changed online and get study permit updated.
If you become absconding from Concordia, then they are gonna report it to CIC. These days they have much sophisticated software applications than yesteryears. Academic institutions can report any thing ranging from your attendance to your grades and what not. If this gets flagged, as some indiscipline incident, in any manner at any level in CIC database then you will have problem in PGWP, PR and any other form of future visas.
Assuming you started program in Fall 2018, I would suggest in worst case, pay one semester/term fees and withdraw from program in legal manner. Paying off few thousands dollars today can go long way in building your future. Money you can always earn back in future but if you get blacklisted in their database then there is no point of return.
Good luck !