'Overpaid' by SFE but I believe I haven't been?

Hi,
I just received a letter saying I've been overpaid by SFE by £3500 but I am pretty sure I haven't. I am in my first year and will be continuing my studies. I applied for a higher maintenance loan last year but because I did not include one of my parent's income, I was awarded the basic loan of £4500. I sent in a PPF2 form at the beginning of March to be reassessed for the higher maintenance loan and after calling, was told that my application was verified and that I'd receive the rest of what I was eligible for in early May. I, however, did not receive a 'Notification of Entitlement Letter' for the new amount. After I had gotten the money, I used it to settle the rest of my accommodation rent and now I've got a letter saying I was overpaid. I need the higher loan for rent and if it's deducted from next year's maintenance loan, I literally won't be able to pay rent at all, let alone feed myself.