100mb of data usage on an iPhone in two months is virtually unheard of. You are the exception. No carrier details data usage like you would like. Heck, when I log in and check my usage with my broadband carrier, all  get is a single value lump some usage figure. Data is "handshake" process where data is sent back and forth in given sessions. Having carriers analyze data packets and detail them would be a very costly process. You would just be back here complaining that the cost of your data plan skyrocketed. Another viable option might be to set APNs for each method of data access, but even that would induce greater costs and technical support for something like that would be a nightmare.