The first point you need to understand is the fact, that students are smart enough to know that teachers cannot stoop down to their level in matters of bullying, insulting or passing crude comments.

This is why I always mention that the culture you set for the class on the first day will decide your success or failure in terms of students respecting you. Most teachers commit the mistake on going soft and also trying to be popular amongst the students. This attitude purely stems from insecurity.

You have not mentioned the extent to which the final authorities can go with regards to disciplinary issues. You need to rule with an iron hand. There is absolutely no point in counselling them. The moment you find the slightest mess up make sure that the student never dares to repeat it again.

Your body language, your toughness, eye contact and way of addressing that student should send a very strong message. 

The moment you enter the class, let the students be on guard with regards to what you are going to ask. You can randomly pick students and ask them to do a small activity, not related to the module. This will ensure that they be on their toes. If you find them not concentrating make them do an embarrassing activity.

You need to set a precedent.