How to make a NPC respond to lowercase messages aswell?

[Kungenn]

How can I make my NPC respond to lowercase messages aswell.

local keywordHandler = KeywordHandler:new()
local npcHandler = NpcHandler:new(keywordHandler)
NpcSystem.parseParameters(npcHandler)
local talkState = {}
function onCreatureAppear(cid)                          npcHandler:onCreatureAppear(cid)                        end
function onCreatureDisappear(cid)                       npcHandler:onCreatureDisappear(cid)                     end
function onCreatureSay(cid, type, msg)                  npcHandler:onCreatureSay(cid, type, msg)                end
function onThink()                                      npcHandler:onThink()                                    end
function creatureSayCallback(cid, type, msg)
        if(not npcHandler:isFocused(cid)) then
                return false
        end
local talkUser = NPCHANDLER_CONVBEHAVIOR == CONVERSATION_DEFAULT and 0 or cid        
local spells = {
                [1] = {spell_name = "Antidote" ,price = 150, words = 'EXANA POX', number = 1},
                [2] = {spell_name = "Berserk" ,price = 2500, words = 'EXORI', number = 2},
                [3] = {spell_name = "Blood Rage" ,price = 8000, words = 'UTITO TEMPO', number = 3},
                [4] = {spell_name = "Challenge" ,price = 2000, words = 'EXETA RES', number = 4},
                [5] = {spell_name = "Charge" ,price = 1300, words = 'UTANI TEMPO HUR', number = 5},
                [6] = {spell_name = "Fierce Berserk" ,price = 5000, words = 'EXORI GRAN', number = 6},
                [7] = {spell_name = "Find Person" ,price = 80, words = 'EXIVA', number = 7},
                [8] = {spell_name = "Great Light" ,price = 500, words = 'UTEVO GRAN LUX', number = 8},
                [9] = {spell_name = "Groundshaker" ,price = 1500, words = 'EXORI MAS', number = 9},
                [10] = {spell_name = "Haste" ,price = 600, words = 'UTANI HUR', number = 10},
                [11] = {spell_name = "Levitate" ,price = 500, words = 'EXANI HUR', number = 11},
                [12] = {spell_name = "Light" ,price = 100, words = 'UTEVO LUX', number = 12},
                [13] = {spell_name = "Light Healing" ,price = 170, words = 'EXURA', number = 13},
                [14] = {spell_name = "Magic Rope" ,price = 200, words = 'EXANI TERA', number = 14},
                [15] = {spell_name = "Protector" ,price = 6000, words = 'UTAMO TEMPO', number = 15},
                [16] = {spell_name = "Train Party" ,price = 4000, words = 'UTITO MAS SIO', number = 16},
                [17] = {spell_name = "Whirlwind Throw" ,price = 800, words = 'EXORI HUR', number = 17},
                [18] = {spell_name = "Wound Cleansing" ,price = 300, words = 'EXANA MORT', number = 18},
                }    
for i = 1, #spells do
    if msgcontains(msg, spells[i].spell_name) then
        if getPlayerLearnedInstantSpell(cid, spells[i].spell_name) == false then
            npcHandler:say("Would you like to buy "..spells[i].spell_name.." for "..spells[i].price.." gold?", cid)
            talkState[talkUser] = spells[i].number
        else
            npcHandler:say("You already know how to cast this spell.", cid)
        end
    elseif msgcontains(msg, 'yes') then
        if talkState[talkUser] == spells[i].number then
            if getPlayerMoney(cid) >= spells[i].price then
                doPlayerRemoveMoney(cid, spells[i].price)
                npcHandler:say("To cast this spell say {"..spells[i].words.."}.", cid)
                doPlayerLearnInstantSpell(cid, spells[i].spell_name)
                doSendMagicEffect(getCreaturePosition(cid), 12)
            else
                npcHandler:say("You don\'t have enough money.", cid)
            end
        end
    end
end
end
npcHandler:setCallback(CALLBACK_MESSAGE_DEFAULT, creatureSayCallback)
npcHandler:addModule(FocusModule:new())

Right now it only answers to the exact way you write for example it says "Antidote". If I write Antidote the NPC works perfectly but should I write antidote or aNtidote it won't respond at all.

Jiddo helped me fix this with one of my scripts a while ago but I have no clue how to do it again.

Using 0.3.6 tfs

Thanks in advance!