Ok so i have a Galaxy s4 and im trying to text my friend who also has an s4 and he is with att. i can receive his txts but he doesnt get mine. i can send txts to everyone else with no problem and i can call him and receive his calls. he had an iPhone before the s4 but we could txt back and forth until about a month ago. this has been going on for almost a month and its very annoying and inconvenient. also I've tried different sms apps and have factory reset my phone as well. any help would be appreciated.