PhoneField.php

<?php

namespace Drupal\telephone\Plugin\migrate\field\d7;

use Drupal\migrate_drupal\Attribute\MigrateField;
use Drupal\migrate_drupal\Plugin\migrate\field\FieldPluginBase;
class PhoneField extends FieldPluginBase {
    
    /**
     * {@inheritdoc}
     */
    public function getFieldFormatterMap() {
        return [
            'phone' => 'basic_string',
        ];
    }

}