You can't change the company's ID on the Portal. 

If the company's ID changes:

• You are invited by a Head Contractor: you must inform the customers who have invited you to use the SY Portal. They can then send us your new company information to create an account for it. You will then receive an invitation to activate the new account.
• You are a Head Contractor: contact your Cegedim Account Manager. So that Suppliers can send their invoices to this new company, you will need to send your suppliers new invitations.