I have broken something, however someone else has caused further damage are we both responsible?

I have broken my phone screen and I have taken it to Vodafone. At the repairs desk I said to the man how much would it cost to replace and DO NOT push on the screen. However he did, further damaging my phone and denied damaging it. Yet he did admit to assessing the damage by doing so. Also the manager also said that he is not an engineer but a sales assistant. So he is not even qualified to assess the damage. So what can I do, is the price of repair spread between the two of us?