She was not listening attentively. However a big OOPs!

I am not happy about my next door neighbor selfishness. My neighbor has a sycamore tree and is not considerate. My yard is covered with my neighbors big leaves for months and has their house up for sale.
I have spoken to them on previous ocassions and they tell me they are ging to cut the tree down, but nothing has occured.
I am lost for words. I don't know what to do or say without getting legal help.
I do not have a single tree in my yard because I hate leaves. I am tired...