I bought two Samsung Galaxy S4 from Dubai in Nov 2013, one for me and one for my wife. I love my Samsung Galaxy S4 mobile phone, most of the time we get along very well, except for one annoying problem. Which occurs infrequently only to my SG4. I send many text messages and sometimes they might fail. I switch off my mobile, ... just curious why this happens to my S4′s and not to my wife's phone. I would be grateful for any one can explain what is wrong with my SG4. Thank you.