Perhaps a bit more detail on exactly what problems you are having and what WiFi equipment you have (make, model, and version) would aid in providing any help.
Have you read these:
Hey I had the same issue, the wifi was working perfectly the first few weeks and then started to slow down, then it suddenly stop working and didnt connect at all. I tried everything, then I madeup my mind to take it to a Apple Store, where they told me my iPod had a defect . Good news is- they replaced it with a new one, ofcourse it was still under warranty. So visit the nearest store before its too late.