What phone? Any difference when plugged into power? Does this occur when connected to a different WiFi router? Did you install non-authorized (cracked) apps?
Note1: Resetting the router helped some.
Note2: When plugged into power, persistent WiFi is normal.
Note3: Resetting Network settings on the iPhone helps many odd issues.
There is a paid Cydia app which disables things on a user-defined schedule, but before downloading anything thoroughly check everything else. Persistent WiFi in standby AND on battery is not normal.