Refund the ESI leave money - staff has sent my attendance wrongly

Hi i am an employee in a school i have taken the leave for one month by the esi doctor prescribed.. i have submitted the doc slips i the esi office and they have paid me the half of my pay.. after some days the esi people asking me to refund the money as my staff has sent my attendance wrongly that I was present all those days as my school org has not paid me my pay and the esi people are asking money to refund... Can any one help me please.

Pl get a revised letter from the school clarifying the position as well as nullifying the earlier letter and submit it to ESI authorities

But the school management is not ready to give the letter

If you get pay-slip, you can use that or can they not at least give you an attendance statement? School shying away from issuing such a letter is not understandable. You can also submit a letter explaining the difficulty you are put to by the incorrect description of your attendance data and seek corrective action.