So couple of weeks ago, a flatmate of mine invited handful of his friends to hangout and have some beer. There was a guy sitting on the floor right in front of the TV. He called me over because he wanted me to open his bottle of beer (I did that for a couple of people using my teeth). I went close to him and opened his bottle. As I was planning to hand the bottle back to him , it slipped outta my hand and fell on the floor. Some of the beer fizzed out on the floor and I noticed his phone lying on the floor, in the puddle of beer. I quickly grabbed his phone and handed it to him to avoid any damage to the phone. After a few minutes, he shows me that there's a black line on his screen but we didn't talk much about it. 

A week ago he starts calling me and my flatmate, asking for the money to replace his phone screen. He calls me multiple times a day and I've stopped accepting his calls. My flatmates told me that I should not pay for the screen and I think the same since his phone was on the floor and I had no intention to damage it. Also, I'm really annoyed by the amount of calls and texts this guy has been sending my way and any sense of guilt is gone because of this behavior of his. AITA for not paying him for the damage? 