Help with /ban command

[JacobC]

This is my ban script.

local default_comment = ""
local default_lenght = 1 -- 1 = 1 hour, 2 = 2 hours

function onSay(cid, words, param)
    local parametres = string.explode(param, ",")
    if(parametres[1] ~= nil) then
        local accId = getAccountIdByName(parametres[1])
        if(accId > 0) then
            local lenght = default_lenght
            local comment = default_comment
            if(parametres[2] ~= nil and tonumber(parametres[2]) > 0) then
                lenght = tonumber(parametres[2])
            end
            if(parametres[3] ~= nil) then
                comment = parametres[3]
            end
            doAddBanishment(accId, lenght * 3600, 23, ACTION_BANISHMENT, comment, getPlayerGUID(cid), comment)
            local player = getPlayerByNameWildcard(parametres[1])
            if(isPlayer(player) == TRUE) then
                doRemoveCreature(player)
            end
        else
            doPlayerSendCancel(cid, "Player with name " .. parametres[1] .. " doesn't exist.")
        end
    else
        doPlayerSendCancel(cid, "You must enter a name.")
    end
    return true
end

Whenever im trying to imply it on someone it says the following error:

[10/10/2009 19:00:00] data/talkactions/scripts/ban.lua:17: attempt to call global 'doAddBanishment' (a nil value)
[10/10/2009 19:00:00] stack traceback:
[10/10/2009 19:00:00] data/talkactions/scripts/ban.lua:17: in function <data/talkactions/scripts/ban.lua:4>

I'm using the ban command like this:
/ban name