Coolwinks.com - Cashback not received

Purchased a pair of glasses from Coolwinks during the summer sale ***% cashback offer which was stated that it will be credited post ** days of delivery. I haven't applied any promo code or Coolcash which makes me eligible for the cashback as conveyed by the customer care helpline desk as well as support@coolwinks.com. I haven't received any cashback post ** days or extended time period even though I repeatedly inquired about it. The customer care has a long waiting period and doesn't pick up even after continuous trying and rarely when they pick up they extend the time of redressal of complaint. There has been no resolution so far and have given me immense mental stress and torture and also the financial difficulty for not getting back the amount at the right time.