I am a Verizon customer with iPhone 8. My friend is an ATT customer with Samsung Galaxy. I can send him messages and call him. He can call me but he is unable to send me a text - they will not go through. They come back as undeliverable. I have been to the Verizon store and they said it was an issue with his phone, he went to the ATT store and was told it was an issue with my phone. Does anyone have a solution to this problem?