Is this a bannable or suspendable offense?

Well, just wondering if somebody can be banned, warned, or like a three hour suspension for this. On my alt, I needed help with a quests, and these 2 people invited me. They were both on the same quest I was, and when we got there, instead of killing the elite I needed, they told me I needed to help them finish 3 other quests and then we would 100% do my quest. So we spend about 20 minutes to half an hour finishing these quests. We finally go outside to the mob I needed, they remove me from the group, ignore me, and go to turn their quests in. Does this fall under some sort of ninjaing at all or anything? I know I just sound like a raging QQer, just kinda mad lol.