Using the Osmocom SIMtrace hardware/firmware/software, you can perform protocol analysis on the (U)SIM card interface between your phone and the actual card.

Such protocol traces can be helpful to learn and understand about the (U)SIM card related protocols, as well as their many obscure features and how those features can become security issues.

Osmocom SIMtrace is an open hardware project with full schematics + layouts released. All software, including host software and USB device firmware is released as Free Software.