Looking to change from Management to Accounting&Finance in Warwick

Hi, I'm an international student with an offer from warwick for bsc management, which I've met and have submitted my exam results to the warwick office in my local city. However, UCAS track hasn't been updated and I haven't received my CAS. But now I think I like the A&F course more than the management course (both in the business department), is it possible at this stage to ask them to change? Should i send an email to the business school or the undergraduate admissions office? And should I wait till UCAS track is updated and CAS is received?

Thanks in advance xx