How to hard reset my nokia lumia 540

How to hard reset nokia lumia 540 

• Switch off the phone and remove your sim card
• Insert battery press and hold power on key in a few seconds.
• Then press power key key once again 
• After press and hold volume down key.
• Release the both key when you see the exclamation mark. 

Mobile Phones Call related All Code

1. Cancel All Divert Call.     

           ##21#     [Send]    

2. Check Status for Divert Call

          *#21#      [Send]

3. All over Divert Call Cancel Code

        ##002#    [Send]

4. Set in Call wating

       *43#       [Send]

5. Cancel for Call Wating

        #43#    [Send]