Like Many others, I too had a very bad experience with Matrix. I asked for a pre-paid internet sim for my tab for my France trip.(I have proof on it. They sent me all the details on pre-paid cards) They said, if the limit crosses 5k it will automatically get disconnected. They took 12k from my C.Card and later tried to bill 36k! I immediately changed my credit card number.
Now they have sent me a legal notice. I guess, we all victims should come together and send a legal notice against Matrix. I think we should also call a press-conference on this matter to aware people.