If you receive a call on your mobile from any person saying that he or she is a company engineer, or telling that they're checking your mobile line, and have you press #90 or #09 or any other number, end this call immediately without pressing any numbers. There is a fraud company using a device that once you press #90 or #09 they access your SIM card and make calls at your expense

Also if you receive a phone call and your mobile displays 'XALAN' on the screen don't answer the call, END THE CALL IMMEDIATELY, if you answer the call your phone will be infected by a virus which deletes all IMEI and IMSI information from both the phone and the sim card.