TRAVELCHECK - they should have negative ratings for companies like this

I have a voucher for flights on TravelCheck. Despite finding the same flights, for the same day on the same airline on another website at 25% cheaper. Tried to contact TravelCheck to query this. Called the number and emailed numerous times with no joy. If I did not have to redeem my voucher, I would NEVER use their services. There are totally unaffordable and a bunch of ******. STAY AWAY!