Swimming pool chemicals stains pool permenantly

On 31 December 2014 I approached Elene's Pools as my swimming pool, at that stage sparkling clear blue, could not achieve the correct Ph. I spoke to Veronica who tested the water sample I provided, and issued me with approximately R500's worth of products which I had to add. After adding everything as I was instructed, I woke up 1 January with a milky pool. After the water cleared it became apparent that the pool shell had been stained a brown colour. After having spend now about R2500.00 at the supplier, they are refusing to acknowledge their responsibility in ensuring my pool is restored to its original condition. They have ignored all my correspondence and promises to visit my property to attend to the problem has not materialised.