Check and see if your pickup wires are feed throuhg a rather large grey cyllinder. Please email your shipping address if you don't have one and it should take care of it.
If you do have the cyllinder (a ferrite bead), then you'll need to send your electronics in for an upgrade.
To reduce the highs, turn the low-pass filter frequency knob (tone control) down. The range is from 350Hz - 6KHz, so if you turn it down, you will eliminate unwanted highs. Also, you might try using only the neck pickup.