well they only have to communicate the change to their own pax and then the agencies,whose responsibility it then is to inform pax who booked their tickets through said agencies. Should the
airline follow up with all of an agency's customers too just to make sure the agency did their job properly? If I go to an agency, be it a brick and mortar business or an OTA, I deal with them alone and I expect all necessary info to come from them. Anything the airline might do on top of that is just a bonus.

Of course the OP got a bad deal here. Of course Priceline and/or the airline could and should easily do something about it. Of course OP deserves a refund. But it kinda proves the point about adding an extra link in the chain. It's just another possibility for something to go wrong or information to go missing, and another set of horrible customer service interactions, bouncing backwards and forwards between companies like a tennis ball.

I really understand the OPs frustration but I wouldn't waste more than a few hours trying to recoup this and I certainly wouldn't contact a lawyer. In the end you will probably waste so much time and there's no guarantee you will get the refund in the end.