If your child is receiving 504 services, but you do not believe their behavioral supports are effective, you should consider requesting an evaluation for special education services. See form 5 on page 36 of the IDEA manual for a sample letter.
If you do not believe that your child needs special education services, consider calling a 504 meeting and request an Functional Behavior Assessment (FBA). See form 6 on page 37 of the IDEA manual for a sample letter.