What constitutes interference with child custody?

My ex husband came to pick up our son on 3-23. I attempted to discuss a clothing issue with him. He allowed his other son to go inside to find his brother so I stepped into the doorway to talk. The stepmother has been dressing my son in clothes that are two sizes too big over the past month and keeping my clothes. Some of the clothes are dirty and stained. I have to change my son's clothes at school. I tried to discuss this with the stepmother on 3-21, but she stated the clothes were fine and closed the door in my face. I called my ex husband that morning but never heard back. 3-23 I tried to discuss this with him. He became argumentative. The boys were running back and forth playing. My son wanted to take an item that I wouldn't allow so he got upset. I tried to calm him down. My ex ended up calling the police claiming interference w/ custody. He said I wouldn't let them leave. The police didn't do anything so he went to magistrate 3-28 for a warrant. Is this interference