Reneging a Summer offer

Last week I verbally accepted a Summer Analyst position with a group similar to the Global Transaction Banking group at DB. I have not signed anything, but I called up the HR rep and told her that I would accept the offer. However, I was just contacted by an Investmet Management group at a different BB about coming in for an interview. I would rather work in Asset Management than transaction banking. In addition, this particular investment management internship happens to be in my hometown city, cutting down on my summer living expenses significantly. If I receive the Investment Management offer, I would really like to take it. However, I am worried about the ramifications of reneging on my verbal acceptance to the other bank. I.E., I don't want to make a bad reputation for myself in the financial services industry before I even start working. Does anyone have any experience with a similar situation? Specifically, reneging on a summer offer to switch to a separate bank and performing a different role (like in my situation, switching banks and switching from transaction banking to asset management)? Thanks for any insight.