KENT RO SYSTEM LTD - AMC End Date Needs Correction

The AMC end date for our Kent RO water purifier is incorrectly updated in the system as **th Feb **** whereas it SHOULD actually be **th May ****.
Per receipt serial number ******* dated **/**/****, Rs. ****/- annual AMC amount was paid as cash. The AMC Start and end dates should have been **/**/**** to **/**/****.
Per receipt serial number ******* dated **/**/****, Rs. ****/- annual AMC amount was paid as cash for renewal of AMC up to **/**/****.
However, Kent's system have updated the AMC End date as **/**/****.
The issue it appears is that the AMC end date was incorrectly updated in May **** itself to **/**/****.
So, when the service engineer came for service on **/**/****, he suggested that the AMC is due to expire soon and we could also make payment for it so that it renews for another year when due. The payment was duly made to him then (refer receipt *).
It was later checked and realized that the AMC payment was made about * months early.
The Kent Customer service was called several times as every time they promised they would fix the issue but they haven't.
Couple of emails (March **th and June **th **** to service@kent.co.in) with receipt proof have also been sent but no reply has yet been received.
Their supervisors have been spoken to too. They all promise to take care of but never do.
We are just tired of dealing with them. Please help get this issue resolved.
Thanks.