I send the wrong item to buyer and he is not replying too

[red_magpie]

If you sent them the wrong item the buyer can use eBays money back guarantee. EBay will enable you to send them a prepaid return label, and refund them on return. If they prefer the item you sent them to the one they ordered they may just keep it. There's nothing you can do about it.

[redwick1]

There is nothing you can do to force them to reply.

Unfortunately your mistake and you will have to suffer the loss.