Customers being misled by DStv price lock

I have been misled by multichoice DStv I took a price lock with them I was promised a free installation as the advert on tv ,Newspapers and Magazine it says free installation .When I checked my statement I noticed that I have been charged R50 installation payment plan which I don't know about ,you are misleading the customers to take up the plan and there's extra charges that the customers are being charged without knowing. Saul ***