You can take up 3rd axis card c2c against icici . Then ask axis to match limit of oldest axis cc to this higher limit. If that card >6m old, then you can Use it for dcb c2c. But you have to wait till higher limit is reported to cibil, which will most likely month end.
1 thing I am not sure. For upgrade to dcb, hdfc ask 5L limit in existing hdfc card. Not sure how much CL is required for other bank cc. You have to check dcb specific thread and ask people who have got dcb in c2c method.