Customer asking for refund for expedited or next dai air shipping

Customer are contacting me demanding I issue the $12.50 for expedited shipping fee or $50 for UPS Next Day Air when they selected the option when they checked out.

I reply to them stating "I am only the shipper and I have nothing to do with taking the order or processing the payment that all done with Amazon. Amazon send me the order along with the shipping label and I just ship the packages. From what I see on my end it looks like you selected expedited shipping service which cost $$$$. There is nothing I can do on my end I suggest you contact Amazon and resolve the issue with Amazon"

So they call Amazon and Amazon send me a message to assist the buyer with a refund of the shipping.

So Amazon sates these are their customers and Amazon is the one talking the order along with whatever shipping option they select. so why am I being left to deal with his? Amazon should be explaining to them they chose an expedited shipping option and if Amazon want to refund them they should take out of their own pockets and not ask me to do it. Why is it I have to deal with Amazon problems. Amazon refuses to take any restorability in any of the matters and of course if I get a negative review Amazon will not remove it.

I know these customer are also playing the game and scamming Amazon choosing expedited and then calling to get refunds because Amazon will give it to them