Turn American Express/AMEX Reward Cards into Cash
If you want the cash you have to go through an extra step. When you get the card(s) call the phone number on the back (1-800-297-7327). You have to input the card number and security code. From the options, select 5 (more options) and then 0 to speak with someone.
You must say the magic phrase "I got this card from doing a rebate, I would like to request a check be sent to me". If you mention the word cash anywhere you will likely be denied unless the CSR is already familiar with this process. If they say they can't do it, then you need to convince them otherwise because they can. Tell them it said you could do this when you filled out the rebate form.
If you have multiple cards they can all be combined into one check. They will give you a confirmation number you should write down in case the check never arrives. The check will arrive within 20 business days.