It's always possible to change your personal details (name, e-mail and password) through the dashboard settings. When you have the correct user rights tied to your account, you can also update the company details used for invoicing.
Go to the billing information settings and adjust your company details. Keep in mind that the information is only updated in upcoming invoices, not in the past invoices that have already been sent.
In case you would like to transfer your account including all the users to a new company/owner, contact firstname.lastname@example.org