Having worked at AMC in the past. I would say inform an usher or customer service. They have the power to toss people for that. As an usher I felt great joy at the potential to kick a disruptive guest out. Usually a warning is given. If a problem is already known an usher might check in periodically to make sure people are still behaving themselves.

It's not a perfect solution. As a lot of times the ushers will literally only have time to clean theaters and not police them. Also in my experience. The assholes always shut up or stop what their doing the moment an usher shows up. But I will say that it does work. Employees are more than happy to enforce no talking/phone rule if they can.