You may want to replace all the people and org data you have, by deleting the old ones and importing new data. For example, this could be done if you want a fresh start to your organization.
You should know that deleting all the data is not possible since the Organization records have activities, invoices, and accounting data associated. Instead, making them inactive will do the job.
To make organizations and people inactive, please create a support ticket mentioning if you would like to keep any or make inactive every single one. Also, attach the data to be imported in an Excel spreadsheet.
Note for agents: Making all people and organizations and then importing new data requires a developer from the Product Specialist team. Please escalate the ticket to them.