If your IMEI is lost for any reason, you can rewrite it without using any software tool
Step 1: Dial * # * # 3646633 # * # * You will be taken to your phone’s EngineerMode.
Step 2: Search for CDS Information
Step 3: Enter Radio information again.
Step 4: When you enter the radio information, you will see Phone 1 and Phone 2. This is for both sims, you will only see one.
Step 5: Enter phone 1 and press E to type AT + in the top AT + field. In the popup menu, select AT + EGMR = 1,7. To find out, dial * # 06 # and you will see the IMEI you entered.
For phones that do not know the IMEI number, enter sim on your phone and go to step 5 and you will see the IMEI number and IMSI number under Send AT COMMAND.