bad service form take a lot.

hi there On Friday i made an order for a pair of wireless headsets,payed for the transaction including the delivery online . i received a confirmation email acknowledging my order and delivery fee.On the email the delivery date was noted as the 10th of December 2018,which i couldn't understand because on the website it says the maximum delivery date is between 5-7 days .i logged onto my profile today to check the order status and it says my parcel is going to be delivered on the 11th of December and not on the 10th.

The headsets are a gift for my nephew for his birthday on the 3rd of December. How do i explain to him that your gift will be late.I need answers to the following questions.

why do i have to wait for more than 15 days to receive a parcel that's supposed to be delivered within 7 days ?' why my delivery date has been change? why do i have to pay for pay for a delivery that is going to take longer than your delivery time under you terms and conditions? How do i tell my nephew that i wont have a present for him for his birthday?