I was using a Matrix Sim card in Europe and initially I had quite an unpleasant experience. My phone could not connect on any network and after endless calls via whatsapp to the guy who sold me the sim, they managed to inform me that the networks were down with all the networks there. I was initially unhappy thinking that this was just another reason they were giving me to escape their bad services, but later when I got a follow up call and a message on the services being fine was something unexpected but pleasant. And to top it up, I even got 5 Euros data credit as an inconvenience compensation.