last saturday, i can send message to my friend. but like after an hour i can't,up 'till now. i tried sending to other contacts but it is successfully sent. so I'm wondering what is the issue? is it the sim card or the number? btw, this number consists of 11 digits and it is the correct number. i already tried adding "1" in the start of the number, switching sim cards, restarting my phone, erasing my friend's number and saving it back, but there's no luck. please help.