Rubbish dumped outside my flat from flats in front of me

Multiple bags of rubbish and other items have been dumped today by Eastern Europeans today. These have been dumped by my rubbish bin and in my bin and I am very unhappy about this, I told them to move it and they could not do this and they said they could not understand. Tbey live above the shops on Hessle road in which the flats back yard backs on to the back of the front entrance of my flats entrance and where we store our bins. This is unacceptable and unfair as I keep this area clean and tidy. This will now cause vermin and has just all been cleared recently. If they think they can just do it they will continue to keep doing it. I have asked them to move it and they refuse saying they do not understand me.