Hi Anand ,
In EL27 you have multiple option .
1. If you want corrected Meter read through EL27 not to be bill do below activity .
Open TCODE EL27--> Correct and release Meter read (Green Flag , Do not press Black one ) ---> Now press Reset button .
So corrected read will be in "locked by agent" and system will not process this meter read for billing , in future you wants the using EL27 you can release it .