draughty windows

Hi, I have been in my rented apartment for 2 years now, there are pvc windows but they are really bad draughts coming through. there were gaps in joins after closing them and i attached a sticky foam to fill these gaps..i didn't contact landlord as i didn't want to bother them as they live far away but i don't want to put up with another cold winter..What could be the problem? one of the window handles doesn't lock down fully either when closed.. What kind of company would I contact about this?Is it a glazier? The landlord normally gets us to organise these things and takes it off rent..I am in Dublin city centre so if anybody has any suggestions of companies ho might do this kind of job i would greatly appreciate it. thanks