I had custody of my granddaughter since she was 3 weeks old. Her mother abandoned her with me after testing dirty for meth

Child protective services placed my granddaughter back with her parents after they have supposedly completed all their assignments. But i have since found out and was told that they continue to do illegal drugs and when i bring to my attention the worker calls me a liar and takes all visitation away for me until the case is closed. My granddaughter is already having issues from them just up and taking her from me. I have had her for a month shy of two years. This child is starting to pull her hair out and bite herself.. biting on door frames cause she is confused and the caseworker refuses to listen to anything i have to say even though i have proof that they are buying and doing the drug and they continue to leave my granddaughter in that safe environment. I need to see who i need to speak to or what i need to do to get her removed from this place asap...