For a rushed example...
Rain smacked on the bus stop overhang. Bob tucked the brightly wrapped present tighter against his side. If even a drop touched his niece's present, he would never forgive himself. A cellphone dinged and, with a sigh, Bob dug into his pocket. The light notification screamed blue, he didn't need to check who it was. He tapped an icon and a message came up:
Where are you are? You're late.
Didn't expect the rain
Bob braced himself for the response, his brother was a stickler for punctuality.
Depending on how long it goes, I would add in some more action to keep it clear when Bob is responding to the text. If it's just two people, it's fairly easy for the reader to keep track of who is speaking/texting but it's helpful to break it up with some action/internal dialogue. So 1) it's not a giant list of texts and 2) it's more interesting (in my opinion)
You could include a picture too, though I haven't seen it done in a novel. I'm not sure if that would be jarring for the reader to switch between text and pictures for a novel format. You would have to make sure everything was legible in the image as well, but it is an option you could test out!