When children disobey it creates stress in the family. The best way to teach healthy communication is to model it. Children learn from what they see and somewhere it has been impressed on them that the way to get your way is to be loud, rude, and oppositional. Kids need and want limits. They feel more secure with parents in charge and thrive best in that environment. Out of control kids hate themselves for their behavior and it shows.
Children seem to learn best when they are rewarded for desired behavior and rewards withdrawn for behavior that is undesirable. This seemingly simple concept is most effective when all responsible for the child understand that brief timeouts or removal of a special toy briefly will not do permanent damage. In fact, the reverse is true.
Children seem to thrive best within established limits set by parents and in school. The best parents and the best teachers seem to have magic when children are with them. They know that consistent, loving expectations are absolutely necessary for a child to learn rules and to get along with the rest of society. What children learn as a child, will benefit them as adults.
The child knows the rules because they are taught reasonably, without anger, shouting or being out of control. They need to understand what the rules are and what the consequences are for breaking them. They are reasonable for both parent and child. When the rule is broken the child is told why he is losing time with the family for 20 minutes or losing a favorite toy for two hours. Decide what is reasonable and follow through. Anyone else responsible for the child's care should be informed of the rules and consequences and willing to participate, or at least not sabotage your efforts.
Maybe grandma didn't do it that way in her day. We live in different times where children are facing many more challenges than in a time that was different and presented its own challenges to parents.
It is important that you explain the boundaries, set the limits, and follow through with the consequences. When all is done, with love and caring you will soon see some remarkable changes in the child's behavior. The bonus is that you will see some real positive changes in yourself and your family as well.