<human>: Can you condense the text into a few key points?

I'm 20, and my boyfriend of a year is 23. I often times find myself getting annoyed at his behavior (in social situations) but never when we're one on one. Here's what happened last night:

We went out to dinner last night. I hadn't seen him in 5 days. We're at a restaurant and in the middle of me telling him something very important (a serious dispute between my mother and I that he brought up) he says "I'm gonna take this call and talk to ____. Ok?" And since the phone was already in his hand, and I was so taken aback by it....I said yes so that it wouldn't cause trouble. 

He was the only one in the restaurant talking on a phone, and the place was packed. To be clear,  I have NO problem with him picking up for his mom (she has health issues) or something legitimately worthy of a call, but to talk to his friend in the middle of our dinner about nothing, I found rude. It was things that could have been answered in text or at least waited 20 minutes until after dinner. The call was only 2 minutes, but it still bothered me that it had to be taken during our dinner. He also frequently texts during dinner, and I've begun to as well, because I find myself caring less at this point, since he doesn't see my side.

I don't think I'm  being uptight. If something bothers me, I communicate it. I waited until we were leaving the restaurant to say anything, and I brought it up in a nice tone. I didn't get angry. He says I'm constantly nit-picking, but to me, this is how a couple communicates. Instead of saying he understood what I meant, he argued and said that there's nothing wrong with it, etc. He gets all snide and says how I think he's immature, and that he'll never be mature enough for me in a sarcastic tone. This happens all the time when I bring up something that bothers me. I don't even feel comfortable telling him anymore.
<bot>: Boyfriend took a not important call during dinner. I told him why it bothered me. Any time I tell him my feelings it turns into an argument. What do I do? Bottle it up?