I have used Matrix for my trips to Europe and have to report:
The service works well for outgoing calls but seldom for incoming calls. The incoming calls are either diverted to a voice mail or do not ring at all and the caller gets a "no reply" kind of ring.
The whole purpose of taking a local number in the country you visit, is then defeated as customers cannot reach you.
Also, they debit the card without authorization for arbitrary amounts like5000 or 10000 even when you have not used their SIMat all. They claim it is for authorization but it actually appears on your credit card account.
They cannot distinguish between credit worthy corporate and first time users. Which means they use the same credit card policy for people who travel on company business and may not like using their personal credit cards.