Ineffective screen protector

On the 08th November 2016 I purchased a Huawei P9 lite contract at Cell C Woodlands. I wanted to buy a tempered screen protector for the phone but was convinced by Kaylagh Van Der Schyff in the presence of the store manager to buy a liquid screen protector as it also protects the edges of the phone at triple the price of the tempered screen protector. The supervisor even showed me her iphone and said she has been using the liquid screen protector for a while and said her phone dropped a couple of times but did not break. After they installed the screen protector I was not comfortable with it and requested to add a tempered screen protector on top but was told its not necessary. On the 3rd July 2017 I dropped my phone and the screen broke. I took it back to the store as it was within a year. After about two weeks I went to check progress only to be informed that theres a quotation for R4444.86 to fix that screen. I informed the manager that I was made to beleive in her presence that the product was fail proof and said she will contact Repair center the following day but did not guarantee they will fix the phone. About 3 weeks later I received a call from the manager that I must either pay the quoted amount or come collect the phone as Cell C refuse to take liability of the phone. I would like for Cell C to fix my phone at no cost as I was misslead by their staff to beleive that im purchasing the best product to prevent the screen from breaking.