def extract_types(transaction):
    """
        Extracts promo_type and service_type
    Args:
        transaction: input from FS chatplan

    Returns:
        promo_type: either U, B, D, G
        service_type: either [local, outside] + [call, sms]

    """
    needed_fields = ['U_', 'B_', 'D_', 'G_']
    if transaction[:2] in needed_fields:
        promo_type = transaction[:1]
        service_type = transaction[2:]
    else:
        service_type = transaction
        promo_type = ''

    return promo_type, service_type