Do you mean AMS to Antwerp?
As this is an international journey, you have to go to
https://www.nsinternational.nl/en/home-1 to price a through ticket
If you can be bothered, it is cheaper to buy a Netherlands domestic ticket (
http://ns.nl) to Roosendaal and then a Belgian rail ticket from there (
http://www.belgianrail.be/) - you can buy these online or at the station (NS machines take coins, or card for 50c extra, and Belgian rail has a card-only machine at Roosendaal)
GVB is for Amsterdam and surrounds only.
Amsterdam Tips implies it's cheaper and faster to book:
http://www.amsterdamtips.com/tips/in...-amsterdam.php
They claim it's 19 euros each way.
I cannot verify for Aug 22 travel.
can you compare for me as the route you suggested does not seem available for AUg 22 date?