Hi,
The ESI contribution period is as below
1st April to 30th September
1st October to 31st March of the next year.
After the commencement of a contribution period, even if the gross salary of an employee exceeds Rs. 21,000 monthly, the employee continues to be covered under ESI scheme till the end of that contribution period and the contribution is deducted on the new salary even if it is above Rs.21,000/-. So for information ESI will be deducted till the end of contribution period irrespective of hike.
If you are the HR of the Organization you may explain the employees as above.
By the by what do you mean by Government list ?