code: func (c *CallService) Update(ctx context.Context, sid string, data url.Values) (*Call, error) {
  	call := new(Call)
  	err := c.client.UpdateResource(ctx, callsPathPart, sid, data, call)
  	return call, err
  }
docs: // Update the call with the given data. Valid parameters may be found here:
  // https://www.twilio.com/docs/api/rest/change-call-state#post-parameters