Originally Posted by
Often1
Correct. It is extraordinarily rare, but there are carriers which, when they can, impose excess bag fees on connections. Example would be a carrier where your status gets you an extra bag connecting to one where you do not have status.
This one was simply a scam. That is why you should report it to DOT.
I believe as far as ticket is purchased in US, your allowance is what is normal for the first segment for that class. (Status/CreditCard giving extra bag of course does not fall under normal allowance). That is your allowance for the entire trip if issued on the same ticket. Now some airlines dont know the rules and end up giving you extra allowance when their own default allowance exceeds what you are lawfully entitled.
BTW, what happened with OP's parents was quite likely not a scam but case of semi-trained not-so-smart staff feeling empowered. Such cases (specifically the attitude) are not so infrequent with South Asian staff at middle eastern airports. What is shocking is that this was done to super senior citizens. Culturally South Asian staff (ground or cabin) usually go out of their way to help super senior citizens.