There was a study that shows systolic BP declined by about 1 mm Hg, while diastolic BP declined by about 4 mm Hg after taking 1000 mg of elemental calcium plus 400 IU of vitamin D3 daily, in 5 years. The effect seems positive, not significant, but still better than the group of people taking no supplements but being active. So taking calcium and vitamin D3 does help.
If you have interests, here is the original paper
However you'd also note that calcium can interfere with some medications treating high BP, including Thiazide diuretics, and Calcium channel blockers.
Calcium supplement does not interfere with beta blocker, ACE inhibitors, Angiotensin II receptor blockers, or Renin inhibitors.
Conculsion: taking calcium and vitamin D3 supplement is helpful to lower BP, but make sure you ask your cardiologist which medication he's giving you right now.