Yes possible and very easy too. just drop a mail to
Grievance.Redressalcc@hdfcbank.com.
But before you upgrade let me tell you some negatives and positives.
Negatives
1) Acceptance issues comapred to visa.
2) High MDR charged by diners network to merchant and some offline merchants avoid these cards, becuase of this.
Positives
1) Wider lounge availability.
2) Faster transaction speed on merchants as observed my me.
and your new card will remain LTF as well.