I had used Matrix phone during my travel to Japan. With it I provided a discount voucher provided with ICICI travel card. During billing two things happened
They used "standard chartered bank’s" "Sell" prices for Yen to Rupee conversion. This conversion price was more than 6% at the market price of Yen. This was not mentioned in their Invoice sent to me. Even after bringing this to their attention, they did not reduce the price. They recover their charges from the deposit taken while handing over the SIM card, so you can’t even go beyond a limit. The deposit is quite heavy.
They never applied the discount voucher I gave to them even after a month and half. Their support is worst of the kind. They do not read the mails propertly and do not answer your queries to the satisfaction. I am still battling with them to get my discount.