I am interested in EXACTLY how the sill plate is attached to the block. Perhaps you can take a picture and post it. With a conventional poured concrete wall, the sill is attached to the concrete using J bolts that are embedded into the concrete approximately every 12 inches (exact spacing depends on code). With a block foundation, normal practice is to fill the block with concrete in the location of the J bolts, and embed the J bolts in the block.
The J bolts are threaded on top, and penetrate through the bottom of the sill plate to the top. The top of the J bolt has a nut (double nut if the contractor is unusually careful). The nut holds the sill plate down flat on the concrete (or block), which prevents the kind of gap you are seeing. Additionally, if there are any gaps left between the sill plate and the concrete, the gaps would generally be filled with foam, fiberglass, or similar material to minimize air infiltration under the sill and into the basement or crawl space.
Sounds like you may be missing the J bolts. That would be a serious problem, since all you are left with without J bolts is a friction fit between the sill and the foundation wall, which is unacceptable.