I am using the code
TelephonyManager tMgr =(TelephonyManager)mAppContext.getSystemService(Context.TELEPHONY_SERVICE); mPhoneNumber = tMgr.getLine1Number(
I think Sim serial Number is unique. You can try this.
TelephonyManager telemamanger = (TelephonyManager) getSystemService(Context.TELEPHONY_SERVICE); String getSimSerialNumber = telemamanger.getSimSerialNumber();
Let me know if there is any issue.