mutation ChangeBillingPlan($input: ChangeBillingPlanInput!) {
  changeBillingPlan(input: $input) {
    error {
      message
      type
      code
      fields {
        field
        message
        type
      }
    }
  }
}

{
  "input": {
    "planKey": "LEGACY"
  }
}

{
  "data": {
    "changeBillingPlan": {
      "error": {
        "message": "string",
        "type": "VALIDATION",
        "code": "string",
        "fields": [
          {
            "field": "string",
            "message": "string",
            "type": "VALIDATION"
          }
        ]
      }
    }
  }
}