Personally, if this is a conversation taking place over text or verbally, there's one technique I use in writing dialogue that helps the scene as a whole. (this is going to depend greatly on your writing style, and if you're writing genre fiction or interpretive fiction) I'm going to guess based on the spelling you used, this is a texting conversation.
Its going to come down to style and preference (again), but personally I don't like reading text messages (on my phone or in a book) when the sender isn't spelling an entire word out. Abbreviations are okay here and there, but if its in the style presented in the example given, its more frustrating.
Another factor that will influence how you execute this, is the culture the characters live in. If they're high-school kids, they're more apt to use this kind of informality and short-cut spelling. Thirty-year-olds? I don't know, maybe a few phrases, but probably not the entire message.
Basically, there are a few guidelines to follow (as you mentioned) but its just going to come down to the specific situation you're using the conversation for. Is text even the best place to be having this conversation? Why not in person? Or why not verbally, where tone of voice can come into play?
In either case, I like to see the characters move around in between sending the texts. Let's say Jane is on the bus on her way to meet a friend for coffee, and Tom is on his way to work, running late and trying to fix breakfast.
“Hi!Who is this pl?" Tom hit send before snatching at the toast after it popped up. He had gotten half the slice buttered before the reply came through.
“This is Camellia Goldsmith.”
Tom paused. Goldsmith?
He typed out an answer, careful not to smear the screen with soft yellow spread. “Do I know u?”
Or we could get Jane's side of it.
Jane's lap buzzed, drawing her gaze away from the street-side view of her window seat.
"Hi! Who is this pl?"
She smiled. "Camellia Goldsmith."
Someone in the back laughed so loud, she started in her seat.
"Do I know u?"
See how we're getting characterization and an attitude along with the conversation? I added a few letters, but kept some abbreviations as well. Again, this is just my style and preference, but you'll have to decide what will develop your story and characters the best.
Does that help? Overall, I would really recommend not leaving a chunk of dialogue in a story or novel.