It is important to understand that economics and finance are very different majors. Economics is a liberal arts course of study and gets very theoretical at the upper levels. In contrast if you go to an undergraduate business school you will take a business core with introductory classes in subjects such as accounting, finance, IT, marketing etc. and then you will major in one of those disciplines. I’m not saying that one path is better than the other, but they are different. I would take the time to look at the coursework (can be found online) for both a finance and an economics major and see if one path is preferable to you. If you want to study business as an undergrad Kelley is a great option to have.
And FWIW for a MBA you don’t need any particular undergraduate major.