This is a new issue for me. I use an unlocked iPhone 5c. I receive text messages from 2 friends, one on an iPhone the other on a Samsung. I send them texts, often within seconds after I received theirs. And they aren't getting my texts even though my phone says the message went out. The firend with the Samsung got a message 24h+ later... I need this fixed!
Yes for years now.
Just sent myself a text and got it immediately.
I had sent my friend G (iPhone) a text w image last night and the respons was quick last night. This morning G sent me a text and I responded but the message wasn't received till this afternoon. Texts between G and I are working fine for now.