Is it permissible to use mediation to rent the university hall for free, knowing that its original cost is five hundred pounds?

If obtaining the hall for free is legally permissible and does not involve trespassing or invalidity, then there is no harm in using mediation, because it is considered a good intercession. Good intercession is mediating to bring about good or avert evil rightfully, and it is a zakat for influence. As for bad intercession, which is striving to obtain what is not one's right or to prevent someone from their right, it is forbidden. Allah Almighty said: "Whoever intercedes with a good intercession will have a share of it, and whoever intercedes with a bad intercession will have a burden from it. And Allah is ever, over all things, a Maintainer."