Can i change my course on UCAS after submitting?

Would I be able to change my course for a University like QMUL from business management to International Relations with business management. I haven't submitted my UCAS yet but my personal statement is on international management / business and was thinking to submit it. This is the only University that I would have a different joint course for. I would only change the course after i know that id get an offer for BM. Do you think this is possible? Please let me know. idk if this even makes sense

Email the Uni and ask if you can send more appropriate PS directly to them - some will allow this but many don't.

Yes, there is an option to switch courses on UCAS for a period of 2 weeks after submission. But I don't quite know what happens or how it works.