Bro I have faced also the exactly same issue.😑😑
Exact reason could be your mobile number that is on Credit Card is different than the account/ or you got Credit Card before opening the account.
I was able to get through it : By first calling the dedicated Credit Card line then send the mail to them.😀😀
They had processed the LE in 1 week.😎😎
But kindly note that whenever backend team will do limit enhancement they will make soft enquiry on CIBIL!!😤😤