Flipkart — i'm complaining about i didn't get my refund money yet but flipkart lies they said they already completed the refund.

Sir/mam i'm naresh kumar naik i have ordered a phone poco x2 worth 18499/- (Prepaid) and i canceled due to late delivery process. And applied my refund query & it accepted by them.
After on 29th june the seller refunded my money to my debit card according to flipkart but flipkart had gave due date on 7th july to complete the process and money will reach in my account. But on and after the due date there is no money i received yet, but flipkart saying we are completed your refund. But till now no balance credited my account yet. What i'll do? I'm very depressed regarding this and 18499/-i is very huge amount for me. Please help me.