I emailed them to their greviance desk, it can be done on the Kotak website. I did through the website.
Or you can also try
grievanceredressal.bankaccount@kotak.com if it works but I still have no clues about if they upgraded it correctly or not, I am not debited 300 charges aswell and haven't even received dispatch details of debit card for about 3-4 days . The support agent told me that I can use virtual debit card for 5% cashback, which I am not sure aswell 😂
So I'd say wait a bit, I will update here in the group, but you can try aswell.
Also, I had to visit branch for change account type.