ESI Deduction - Employee Wages

I heard that ESI is mandatory for the employee who is drawing wages less than 15 K.
My salary got revised on june 14, (+15k Now). Still ESI is deducting from my salary , HR are is saying that ESI can not be stopped.
Can somebody help me to explain this to my HR ,Is there any act / law written on this

Please share any circular reference based on which we can STOP contributing in the same month, if the salary increases beyond ESI Limit. It would be helpful to many people who go by rule book.

Sir(s),
1. The copy of any circular which is desired by you is not available since by virtue of provisions contained under section 2(9) of ESI Act, 1948 read with Rule 50 of ESI (Central) Rules, 1950 employees are deemed to be covered till close of respective contribution period.
2. However, while calculating Rs. 15000/-,per month, please ensure that the amount does not include Over Time. On the basis of OT an employee cannot be exempted.

Dear Friend,
You are well are that ESI ceiling limit is Rs 15000/ per month on gross salary, If a person is drawing a salary not exceeding Rs 15000/per month,he will be covered under ESI Act and ESI contribution shall be payable on the gross salary at the applicable rate (Employee @1.75%. & Employer @4.75%). In the ESI Act, there are two contribution periods ,i.e. April to September & Oct to March.
Your salary got revised on and from June and as such you are falling within the contribution period March to September due to which ESI contribution shall be deducted till September.
Your HR Dept will stop deduction of ESI contribution from your salary with effect from October.However, it is to be noted that you will continue to get medical facility from ESIC till end of next contribution period (October to March).