If you have an iPhone 6, 6 Plus or older, it will not pair with a new Apple Watch. The new Apple Watch Series 3 and 5 require an iPhone 6s, SE, 7 or newer running iOS 13.
If that is your situation, then
Apple Holiday Return Policy (Purchase between: 15-Nov-2019 thru 25-Dec-2019, Return by 8-Jan-2020)
All purchases made before November 15, 2019 and after December 25, 2019, are subject to the Standard 14-day Return Policy.
https://www.apple.com/shop/help/returns_refund
If you have an iPhone that will work with your Apple Watch, then please give more details.
What Apple Watch Series
What watchOS version
What iPhone model?
What iPhone iOS version?