I would NOT AT ALL recommend Matrix sim card.
I was travelling to US for the first time and while travelling from IGI Airport I came across their Booth and took a pre paid sim card from them. They told this is AT&T sim they are providing and as I knew about AT&T being one of the best in US I took it without giving a second thought. Do Not believe when they say its AT&T of T-Service, its NOT!
My trouble started when I landed US, the Sim card was active on time but the services are horrible, I had taken a card with Free India and US calling so everytime I call there is aways a lag, there data service is never connected and is always fluctuating. When I contacted AT&T they said its not on their network, and when I called MATRIX most of the time noone picks up the phone or if they pick up they conveniently give you a Complaint number and tell they will arrange a call back which never happens.
I thought of PORTING my number to AT&T to which AT&T said MATRIX has not AUTHORIZED AT&T or any mobile services to PORT this number. Clever isnt it! Because I already gave my number as contact at Bank/SSN office/My work and am supposed to receive communication over phone. Now, I am stuck with this for a month and cannot do anything about it.
My only advise to people thinking of buying sim card from them, please DO NOT. Alternative is buy International roaming pack on your Indian Sim card for a day or two and then when you land in US buy a Sim card. That would charge you a 1000 Rs more without any pain which I am still going through.