Who makes Diltiazem?

There are many generic versions of diltiazem. E.g Cardizem is made by Biovail Laboratories International.

http://companies.windhover.com/Content/Company.aspx?CoId=27041

Other manufacturers:

Mylan, Teva Pharmaceuticals, etc.

do you mean diltiazem?
Generic Name: diltiazem (dil TYE a zem)
Brand names: Cardizem CD, Cardizem LA, Cartia XT, Dilacor XR, Diltia XT, Tiazac

Here is the link https://www.drugs.com/diltiazem.html