What am I supposed to do?

for enrollment, just take the letters you currently have so there's proof alone of you applying for funding and then tell your uni that your in talks with student finance about amending the amount.

if your parents are under the £10,000 boundary you should be getting like £6000 for the year with grants etc? have you tried doing a current year assessment? were they earning more a couple of years ago?

It sounds as though you've been non-income assessed. Have you sent them evidence of your household income?

You just have to keep hounding student finance. I've had some issues with them but nothing like this. Their system is pretty crap and they get computer glitches inside the system that they can't do anything about other than fix it manually which is probably why it's taking so long for them to sort your problem out.
Get on the phone to them and don't put the phone down until you know the person on the other end is going to sort your query out. What has probably been happening is that the people you've been speaking to on the other end of the phone have probably just thrown your query into a pile of 'things that need doing' and then your query is getting lost in the system or forgotten about. Don't give up and keep ringing them. They have to get it sorted at some point.

Their systems are crap but I think this is just taking the pee now XD
I've been on the phone for the last 4 weeks to them and I've had no results, they only recently found out that someone hadn't read the flag for my parents P60's again and this was about a month later after my loan had been cut down my £2000 but when I was originally phoning them it was to try and sort out my tuition fee but no one seemed to know what the hell was going on D;
I think every operator there knows who I am by number and my name now with the amount of times I've phoned up XD