PhoneField.php

<?php

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

use Drupal\migrate_drupal\Attribute\MigrateField;
use Drupal\migrate_drupal\Plugin\migrate\field\FieldPluginBase;

/**
 * Migrate field plugin for Drupal 7 phone fields.
 */
class PhoneField extends FieldPluginBase {
  
  /**
   * {@inheritdoc}
   */
  public function getFieldFormatterMap() {
    return [
      'phone' => 'basic_string',
    ];
  }

}