My phone won't let my text messages receive to my boyfriend's phone in Sri Lanka! Help.?

I am on vodafone $29 jumbo cap. I have friends in Fiji who receive my messages all the time, so what's different? I have the correct codes for messaging in Sri Lanka and I've tried messaging by replying and by creating a new message but it won't work!! Normally I get delivery reports sent to me once the message is delivered so that I know the person is got it. Thing is, I can send the messages but then he doesn't get them and it's very annoying! Can someone please tell me how I can fix it??