Payments that increases balance owing!!!

I had an account with Boston College that was referred to Hybrid Collections who then contacted me and asked me to make payment arrangements, even though I argued that I did not owe Boston College since I was no longer studying with them. I then made an arrangement that commenced from 2019 if I am not mistaken. I asked for a statement this month only to find out that the balance owed is increasing instead of decreasing. when I asked for a reason they gave me a lame excuse. I am no longer interested in any sort of explanation, I just need to know where is my money gone to? I do not even owe Boston College to be precise.