Asus India — Mobile speaker damaged when mobile submitted to change port

Address: Pune, Maharashtra, 411028

My Phone was have charging issue so I have submitted my ASUS Zenphone 2 to service center in Pune . They have asked me to changed port after my confirmation they have done that and I have recieved mail that mobile is done and i can collect it from service center, When after 2 days i visited service center they said mobile was not yet checked.
Again when after 3-4 I went to collect mobile after coming home i found that speaker were damaged when mobile was submitted to service center.

When i again went to service to report this issue they are saying that I will have to pay 900 Rs to repair that speaker even if it was damaged from there side.
Please help me this is very poor service.