UCAS halls of resident

If I've accepted an offer for uni but would like to change my status of living in a halls of residence, how could I do that?

I've contacted the uni and they've said that I've got to change the status on the UCAS website, which I don't know how to do. I don't want to un-accept the offer and accidentally reject it.

That answer on the UCAS form doesn't go anywhere or do anything. Regardless of what you put, you can chose whether to go through the uni's accommodation process or not. Saying that you would live in halls on the UCAS form does not commit you to anything.

The main problem is that the specific Uni only accepts people into their own halls of residents through UCAS. I was wondering if there's an actual way of changing the form?

(But thank you for your response btw)

That's... bonkers and I've never heard of a uni insisting on it being done that way around.

In that case just give UCAS a call tomorrow, they'll be able amend your answer. Then call the uni back to confirm.