Freecharge.com — I have done online balance with promo code

Address:

Surat, Gujarat

Hello I have done balance using online payment site freecharge.com at payment time i have a used promo code " HDFC2020 " there ( see attachment ) 20% off. look attachment deeply there is validity no more terms and conditions. but freecharge.com given just 20 RS not 20% on balance amount 105 X 20% = 21 215 X 20% = 43 Total = 64 but those give me just 40 so freecharge.com doing fraud works again to customer. here i hope u are take positive and give me proper answer what i can do ? thanks