Try a different design.
Try a different type of area (council, standard houses, mansions etc).
Make sure the 'call to action' on the leaflet is clear.
Consider having a mobile number AND landline.
Is you company based in the same area as the areas you're dropping (some people like a company close).
There's so many factors - I think getting it right to begin with is extremely important before you go out and drop 1000's of leaflets.
But fair play to you, go out and do it! As some other people have said calls will drip by occasionally down the line - and your 'brand name' will possibly be on there mind - which is always good when you eventually door knock (perhaps after Xmas).