I used Matrix Sim card when I went to Dubai during the Dubai Shopping Festival. Every person requires a contact number when abroad and Matrix worked very well without any problems. I sent an inquiry message to Matrix and got a instant call back from them. A person from Matrix will come to your place and give you your number and the sim card.
The payment mode is- they block Rs.5000 on your credit card and on return of the sim, you get a customized bill and the amount of bill is deducted from the credit card and the Rs.5000 earlier blocked is released.The service was very good. No problems at all. I could use it from the moment We reached Dubai til the flight took off for Mumbai.
Also the rates are very cheap as compared to others like Vodafone. It can be upto 75% less than Vodafone. We were charged Rs. 38 for every minute call made to India and the same in Vodafone was about 158 or something.
All in all, they provide good service.I would go for it the next time I go abroad.