How to get limit increased on HDFC cards? Spent 12L + in 9 months yet limit is 7.65L

The title says it.

HDFC has not been increasing my credit limit even when I constantly spend 4L+ every qtr. I have Diners black metal and Tata Neu Card (Spends on this are additional and should be around 3L separately).

I have sent multiple emails, which increased from 7.12 to 7.65 this July. This is despite holding a salary account with Imperia Banking. I would appreciate any ideas.