If the domain you want to register is already occupied by another user, you can choose a different domain name, or some variant of the desired name. This is achieved by minimally changing the letters that make it up. It is very common to solve the problem using something as simple as a hyphen ("-").
For example, if your business is called Mi Empresa S.A., and miempresa.com is already busy, you can try:
*my-company.com
*mycompany.com
*mycompany.net
etc.
If you find more than one variant available, you can take the opportunity to register it. This way you will prevent a third party from registering a domain similar to yours, and you will be able to take advantage of the many advantages that come with multiple domain registration.