I have used one matrix sim card for Japan. While giving SIM Card, one guy told me it is a prepaid one and for Rs. 3000/- I’ll get some free minutes and 100MB data connection. But, another guy gave me a postpaid connection. I made max 9 mins. call international and 6-7 min. local. Within 3 days, 5000/- got blocked in my card. In Japan, I have turned ON wifi in hotel and used WiFi. Normally if WiFi is ON, mobile data will get turned off. But, with matrix SIM card, data connection remain ON and I noticed it on 3’rd day and turned it off. After returning the SIM card on 7’th day after taking it, another 5000/- got blocked on my card. After repeated request I haven’t got any temporary invoice. As they are continuing blocking money on my card, I got scared and had to cancel the card. After a month, I got call from their legal office and still that point I haven’t received any invoice. On request, finally I got invoice and found I had been charged for Rs. 6500/-. According to them, I have used 180MB data, which to me I have never used. So, beaware of Matrix SIM card. Better use some other or use their prepaid one.