I leave up to you advisability of deleting calls, which are the record of work that has really been done, and is the raw material for future management decisions.
That being said, you have several options.
1. Use the Web API to develop the functionality.
2. Manually delete a person who is referenced elsewhere. You should see the list of references and have the option to remove those referencing items (deleting them). After deleting them, you are given the option of deleting the person.
3. Updating the database directly is, of course, unsupported, fastest, and with the highest risk of error.