Activation of $100 iTunes Card

This is going to be a long one, please bear with me. (this is also I believe, my first post here)

Okay, so back in August, my elderly grandparents were taken advantage of when they were called by a group of tech support scammers claiming to be from Microsoft. Flash forward about a week, and they bought 2, $100 iTunes cards off Amazon, which the scammers claimed were "payment cards," and they presumably would read the code off of the back, and use it to steal money.

Anyhow, with the help of local authorities and the phone/credit card company, we were able to stop this before the evil happened. (they didn't get paid 😀)

That said, we now have 2x $100 iTunes gift cards from Amazon that we would like to spend on either music or movies for the grandparents, as they rightfully feel cheated and upset.

However, when we went to redeem them via iTunes, it gave an error that the cards were not activated successfully/correctly, and that we would have to contact Apple Support for more information. I decided to post here asking for advice before calling, as it seems like this is quite the common scam maneuver.

Thank you all for bearing with my abnormally long posting here, and I hope that I can sort this out correctly.