"Health visitor please help"

Our 4 year old obviously has problems. His speech is poor, his behaviour can be erratic. He is always tripping up and school want to give him special help to coincide with speech therapy but we haven't managed to get this for him yet. We have been trying for eighteen months to get him help. The health visitor doesn't return calls. He's had three hearing tests with no problems found. The HV said eighteen months ago that she had concerns about him but we have had no progress. He's been referred for speech therapy and dismissed but he still cannot be understood most of the time which increases his frustration. We know he's got problems, school knows he's got problems but he has to be referred by a health visitor who doesn't return our calls.