Ok, sorry if I wasn't being very helpful.
It would be good if you let us know what kind of shoe it is, or better yet just post a picture of the shoe, or even better yet post a picture of the shoes with your feet in 'em. The abrasion on your heels can be caused by two things, heel lift or just bad/unsuitable design(top-line might be too low). If it's the former, there is hope because your shoes might just need some time to break in, but there's also a chance the problem becomes worse if the shoes are already too big to begin with. If it's the latter issue then just buy heel liners to cushion your feet.
Lastly, are you wearing socks with your new shoes?