How do I know if modifying a court order against the defendant is mandated?

I am trying to modify a court order with an attorney in reference of child visitation. My father is the sole managing conservator, however, the court order accentuates that it is under my father's discretion in regards to visitations with my child. Unfortunately, my father has been taking it out of context and/or is abusing the power of this. I am trying to get in contact with someone who can better explain how I can pursue this matter such as, what type of petition do I need to file to enforce visitation rights and/or what type of file to I need to petition?