Uni has sent me an invoice of 9k

Student finance we’re processing my application because they were looking at my long residency evidence. I provided them with everything they asked for but evidence was still being processed for months. I’ve sent them every letter to prove my residency but when I called SFE they told me they don’t have evidence for a certain date. It’s been tiring to constantly send them letters upon letters and they are still not satisfied. But last week I sent them my most recent evidence which was indefinite leave to remain BRP which I recently received. They said it will be processed by 6th November, but my uni have sent me an invoice anyway with the payment terms being immediate. I am not paying 9k. This has been quite stressful and has given me extreme anxiety. Also received a threat that they will exclude me if I can’t pay this. Wish student finance could work faster or do something on an urgent basis. I’ve told uni my situation multiple times but they still issued an invoice which is so ridiculous.