Hii dear

The procedure for accepting the alloted seat includes downloading seat acceptance letter, uploading the documents and paying the seat acceptance fee. If you did not pay the fee then your alloted seat stands canceled. You will not hold any right over that seat. However you are eligible to attend further rounds of counseling. Your documents too, will not be considered for verification if the fee is not paid.

For further details you can check here

https://engineering.careers360.com/articles/csab

Hope this helps

Your seat is not confirmed if you hadn't pay seat acceptance fees