Why Won't Itunes Assist Me With A Card That Does Not Work?

I bought my son an iTunes gift card from Walmart.  It doesn't work. I have gone back and forth with iTunes tech support, i have set up the account.  Everything is all ready to go except when i enter in the code on the back.  It doesn't work.  I have three other children in the house that had no problem with their iTunes card. The tech support keeps sending me automatic emails to instruct me of what to do .  I have done all that. The card still doesn't work.  I would like it if I could speak to an actual person. I called customer service and they said they could not help me.  What kind of a company is this?