No software is perfect, particularly not when it has to interoperate with mobile device from many different manufacturers, all of whom may have a slightly different interpretation of what the GSM specifications say. This talk will show you what you can do to investigate any issues you may encounter. It covers topics like the comprehensive Osmocom logging infrastructure, taking protocol traces of the various interfaces and GSMTAP. It also informs you how to report your findings to the development team in a way that provides them all they need for hopefully fixing the issue.