Flipkart — Later delivery of Mobile Samsung f41

I have paid cash on 18 Oct. At the time of payment, the delivery was showing as 20th Oct. Now they are changing dates when I contact them for status. Its 4th Nov now still not sure when will it get delivered. I have postponed my travel by a week, still no t sure when will it get delivered. Today it is showing to resolve by 7th.if I don't get it by 7th, then will cancel n want interest on amount paid to them for a month