was told my appletv is defective , can exchange for new one. seriel number dy****rhn.

That appears to be an Apple TV (3rd generation) a.k.a. A1427.

Even if it has truly defective Wi-Fi (unlikely, imho), it will be out of warranty, and exchanging will cost you.

You can take it to Apple for diagnosis. If they can get it to work on their Wi-Fi, then they will say nothing’s wrong with it.

A newer model will cost you the regular retail price.

There is a ‘repair or replace’ program for defective units, for the same model (no upgrade), at standard fees.

Hello,

Firstly it is never a good idea to post your device’s serial number on these public forums.

Who told you your Apple TV is defective? Can other devices in your location connect to your Wi-Fi network? Are you trying to connect your Apple TV to an enterprise network (school office) or a home network?