My Samsung Alias SCH U740 will not txt other...

Question

i can txt other verizon phones but it wont txt other carriers.it says msg sent but it doesnt reach the designated party because they never recieve the message like the normally would.i have unlimited texting so thats not the problem.ive heard that i need to reset my phone,get software upgraded,and ive heard that it wasnt my phone.it has to be because my friend has the same exact phone as me and he was FWDing messages for me to people.(his alias had the same problem and his was newer than mine when it happend.he just got a whole new phone.i dont want to do that bc i have ringtones adn music on this one)

please let me know if you know anything about this problem