Discrepancy in OSAP Dept and Registration Dept. of College.In OSAP I am full time and received full time OSAP T4A 105,In Reg. Dept. I am part time..Shall I pay tax?

Discrepancy in OSAP Dept and Registration Dept. of College.In OSAP Dept I am full time and received full time but In Reg. Dept. I am part time.Now CRA has mailed me that I have to pay tax for box 105 T4A because I have been part time ..

I have been student from sept 2017 till Dec 2018.

I assumed from the beginning that full time is full time in all sections of college but now they have different meaning for full time and part time..They do not take responsibility and I do not know what to do with this tax claim from CRA?Who is responsible for this problem?