Conceptually, you might consider a Person table -- and then identify separate Contact,Supplier, Vendor, Customer....using the PersonId as the link back to the Master Person table. Sort of a master lookup table.
Many Organizations have a master, authoritative Client table. Where ever Client is used in systems, there is a tie in to the authoritative table.
Could be worth considering if duplicates are an issue. But it's a change in data management practices, and would reqire a fair amount of discipline and buy in. The prcticality of this would depend on the severity of "duplicates" to the business.