Unable to use Apple iTunes card as it says already redeemed

I have two Apple iTunes card, which is very hard for me to use because the first one I bought was hundred pounds and they told me there was no money on it now today I just bought another one of 50 pounds and they said it’s already redeemed. I don’t just understand what’s going on. I’m really getting very mad about this. Please just do some things to help me. I can’t lose this money. I need it badly.

[Re-Titled by Moderator]