MTS / Sistema Shyam TeleServices [SSTL] — Unlimited recharge done by mistake due to problem in my wallet, not getting refund

Address:

Dadra and Nagar Haveli, Dadra and Nagar Haveli, 396230

Im sakthi dharan, and mu mts data card no is [protected]. On april 14th i have recharged my datacard using my mobiwik wallet for rs.999 (10gb day and 10 gb night), as it shows transaction failure error, i recharged again, few minutesd later i was shocked to see that my amount has been deducted 2 times.
When i called the customer care, im getting the reply that my first data recharge has been overwritten by the second recharge. So i can get only the benefits of second recharge.
1. They have not mentioned anywhere that carry forward feature is not available.
2. Such kind of problems are not available for post paid customers, then why prepaid.
3. They are saying that there is no refund available, then atleast i should get my data back, 999 is not a small amount that can be simply taken and said that your request has been denied.
4. Each and every data providers are providing carry forward plan, if not then atleast previous data should be added to the newone, but nothing is done in yourside.

I demanded for refund, in the form of money or data. But i simply got the reply that "your request has been denied by the backend".

Did i ask for their money?, im just asking them to give me back my money. But they are just repeating the same answer again and again. Which is making me irritated