What is SI-UK?

One of my parents signed me up for it recently because I needed some help with clearing. She told me she signed me up to get notifications from Warwick, but I think the site somehow lead her to sign up for SI-UK. Regardless I didn't worry too much.
The next day they call me asking me what university I want to go to and when I want to start, and they had no issue with it. I tried doing a quick Google search while on the phone with them and I thought they were for international students getting into uni.
I asked them "Is this for international students only? I'm a home student."
The person on the phone replied "We also serve both home and international students."
They asked for a fee for their charge (I think £300?), but I was really taken aback by how 'easy' they just made it look as if they can just get me into any university. I don't know the entire context and I'm not progressing very far with researching them and if they have some sort of 'catch'.
They called me only 20 minutes ago. If anyone can help me understand this company, that would be great. Thank You!