For all them ho can’t send message, is the only problem that You have to go to your Operator network and to reorder your Sim cards. Because I hade the same problem then I understand that changing my old sim that I bout before 4-5 years, is old system and now I have the same number but new Sim card that support my Iphone message. I tested and it is working, I truly mist my message, but now I will not mist the words coming from my Iphone like, ”Error sending message failed”.

Have Fun with messages.