Hi antoninimarcos,
Thank you for your purchase.

Yes you can change that, but you need to modify some file in core of the plugin. In file wp-content/plugins/ameliabooking/src/Infrastructure/WP/config/Roles.php around lines 90, 103 and 120 you will find this

#Line 90
'label'        => __('Amelia Customer', 'amelia'),
#Line 103
'label'        => __('Amelia Employee', 'amelia'),
#Line 120
'label'        => __('Amelia Manager', 'amelia'),

and you need to remove Amelia from label like this:

#Line 90
'label'        => __('Customer', 'amelia'),
#Line 103
'label'        => __('Employee', 'amelia'),
#Line 120
'label'        => __('Manager', 'amelia'),

After those changes you need to deactivate/activate plugin so changes will be applied.

Please note that this will be overwritten in next update so you need to do it again.

Best regards.