Currently there is nothing much you can do to even know if you are a victim of SS7 Hijacking as demonstrated here . The only way you can know if you are part of such Hijacking is to manually monitor your Network SnoopSnitch
What is SnoopSnitch
SnoopSnitch analyzes mobile radio data to warn about insecure network and mobile threats such as fake base stations (IMSI catchers), user tracking, and SS7 attacks.
How to use SnoopSnitch
To use SnoopSnitch, a rooted device with a Qualcomm chipset is required. Unfortunately, custom ROMs are often unsupported at the moment as they can lack necessary proprietary kernel module. (Some successful CyanogenMod installs have been reported and Sense Custom Rom also showed positive feedback)
This application uses data contributed by other users. By choosing to upload your measurement results or security events, you can help improve this data base and support future research.
Install SnoopSnitch and let it run all the tests , Its a detailed free app to show if you are being hijacked using any imsi catchers or through SS7 attacks