You could create a behavior plan for those students who you are constantly having problems with. The behavior plan would break down your day into subject areas, and students could receive a sticker for good behavior for each. If they earn so many stickers, they receive a prize at the end of the day, and they could take their plan home for parents to view. I think if parents were notified of both the good days and the bad, they may be more willing to support you on the days in which their child doesn't quite follow the rules.

To the parents that you call frequently I would call them when their child is doing a good job as well. Parents are sometimes like students, if you only talk to them about what they are doing wrong, what you are saying might just go over their head after the 5th call. But if you call just to let them know that there student did great today, it will make them want to be involved and they know there student is capable of being good rather than always being bad.

Make sure that you have figured out what motivates those particular students. For each student the motivating factor may be something different. It could be approval from you, a reward, extra credit, "free time" to work on something else they enjoy, drawing, reading, etc. Make sure to catch the students doing something good and reward them with something that motivates them. This may cause them to shift their behavior towards making better choices in class. Also, make sure that you consequences are effective, meaning that they are actually consequences for those students. If calling the parent doesn't work, you may need to implement other consequences for those students. Also, make sure that you are communicating positive things to parents and not just negative things. This can have a great impact on your relationship with the parents and their willingness to help you.