Mandhana Industries / Being Human — why you charge double time gst

Address:

Ajmer, Rajasthan

I did shopping at your ajmer store on 30th dec 2018.in your bill you charge double gst.
Kindly answer me if my goods price is mrp 3699 rs which includes gst b all taxes then 50% discount on it make it 1849.50 which also includes tax than why charge again 12% gst??
Note - if mrp 3699 your is 3255.12 rs taxable amount. It means you give discount on 3255.12 which means taxable amount after discount is 1627.56 rs than add 12% gst on 1627.56 rs than it will 1849.5rs (Includes all tax) after why you charge again 12% gst??
Who give you write to charge double gst??