Warning light to show tow ball is correctly located not working on retro fit swivel towball.

Hello Briskodians, I am fairly new to your forums and have followed some of the topics relating to Superb Mk3.  I hope it is O.K to ask a question relating to the Tow ball topic.  I recently had a swivel ball fitted to my Mk3 Superb, at a cost of £1200.  I have only used it for a round trip to Scotland of 640 miles and had no problems at all, it towed really well.  My only problem is that the warning indicator light doesn't work at all.  I queried this at the Skoda dealer when it was fitted and they  just said " oh well it doesn't work".  Not happy with that answer I contacted Skoda after sales.  They 'elevated ' my complaint to the Technical Team.  After five weeks and several phone calls their reply was that the indicator light cannot be made to work on retro fitted kits.  I find this extremely puzzling as they fit a new wiring harness from the front to rear of the car and a new control module.   

Surely they don't leave out one wire that would power this safety warning light?  Has any one has the same problem after a retro fit?

The Tow ball does lock in place with an obvious 'click', but for £1200 you would think they could include the safety warning light!!

Thank you.