'Strip out unnecessary characters from the string:
+()- & space'

@staticmethod
def sanitise_phone(phone, channel_id=None):

    settings = current.deployment_settings
    table = current.s3db.msg_sms_outbound_gateway
    if channel_id:
        row = current.db((table.channel_id == channel_id)).select(limitby=(0, 1)).first()
        default_country_code = row['msg_sms_outbound_gateway.default_country_code']
    else:
        default_country_code = settings.get_L10n_default_country_code()
    clean = phone.translate(IDENTITYTRANS, NOTPHONECHARS)
    if (clean[0] == '0'):
        if (default_country_code == 39):
            clean = ('%s%s' % (default_country_code, clean))
        else:
            clean = ('%s%s' % (default_country_code, clean.lstrip('0')))
    return clean
