Soy is naturally high in calcium and really doesn't need any added.
Calcium carbonate upsets the stomach acid levels, can result in the blood becoming acidic and calcium taken from the bones to bring blood acid levels down. I read that years ago on the printed page, and cannot even remember the source. It was certainly true for me. I had a series of stress fractures when I was taking high doses of calcium carbonate (doctor's orders).
I haven't researched the newer calcium supplements (the last 7-10 years).
Personally, I feel that foods are the best sources of calcium.
Sesame seed, leafy greens (even iceberg lettuce), cabbage (and its relatives), soy(if you can tolerate it), herbs/teas (parsley, raspberry leaf, nettle) and others. Do some research. Hide calcium foods in everyday things (I like parsley for that).
The calcium guidelines keep increasing, as does osteoporosis. Makes me wonder if calcium supplementation is good. The ancient Chinese had low osteoporosis rates, and did not consume dairy or supplement. They ate soy, sesame seeds and greens. Just a thought.