Hello - according to my experience there are two ways:

1. Export the contact(s) - change the value of the phone number field as you like - import the contact(s) back in Odoo (if the record is imported Odoo will not change the format of the field - as Chris Parker stated).
2. If I'm creating a new database immediately after creation - before doing anything else - I uninstall all apps / modules I don't want - in this case it would be "phone_validation". But be carefull - you can't do this later! without damaging the database / your installation ...

Regards ECF

Thanks for your help.
I don't want to remove spaces. I want Odoo to respect the format that the user has entered.