Phone sent in for repairs damaged

I booked in my iPhone 6s at Somerset West istore for battery replacement. Although there was a scratch on the screen and a few minor marks on the case, the service agent at istore said the battery will be replaced as the screen only has a scratch on it.

Now core group is refusing to replace my battery due to a cracked screen. I asked for a picture and suddenly the screen is indeed cracked and seems like pieces of glass missing. This was not like this when I handed it in so either somebody at the store dropped it or it was dropped in transit to JHB or the JHB staff dropped it and won’t own up. Either way, istore or their agents damaged my phone and now want me to pay R6000 to fix something that was not broken and almost looked new. I even have the book in slip which refers to te scratch on the screen and definitely no “cracks” or other damage to the screen. I have asked a manager to call me and instead I get an email from Elizaan Swart. I want this resolved urgently as the phone was damaged like that after given to you.