fuck this job.com

I work in a customer service department with two other people who sit directly behind me. They use instant messenger constantly and whenever they want to talk about someone, usually me, they will start typing away, while laughing at the same time. Funny, when I turnaround to ask a question, it suddenly stops, then resumes when I turn back to my computer screen. Interestingly enough, these two ask me why I get so focused on the work at hand, could it be the IM'ing that they are doing?
Any thoughts on how to handle this? It is really starting to annoy the hell out of me.