I applided for 4 add-on cards 2 weeks back. (2 mariott and 2 swiggy)
I got all of them different card numbers & different CVV.
To answer your question - cancel/close your existing add-on cards, and apply newly.
You will get different numbers either you apply by calling customer care, or applying via HDFC mobile banking app.
(Easier option is to apply via app)
Please mark as solution if this helps.