procedures on how to view a hidden number on your phone screen

It's every important to see every Gsm user enjoys the gadget he/she has bought or gotten for him or herself. There is always a priority when someone is using a particular device for him or herself. Here I've discovered on how to view a hidden number which might've been in some certain devices which one may not want to be identified as he or she may call you or i. What you have to do to know if someone has been hiding him/herself calling your phone, first of all dial *#30# to activate your phone. Therefore if anyone should call your phone without being identified who the caller is,don't pick up the call,wait about 10 to 15mins and then dial *#30# and you'll see the phone number whose identity wasn't shown while calling you earlier. Thanks for your cooperation