If you wish to go for BA with Mathematics course i.e., combination such as Geography, Economics, Mathematics etc then you have to take some risk. You have to cancel your admission and then have to get admitted in the BA course, in order to pursue your dream. Now it may cause you to loose some of your time, but it would influence you to achieve the field of your interest. So some times we need to take risk for the better good.

I hope this helps.