For that you have to cancel your old pass and buy 1st class passes Usually Eurail charge for that then a 15€ exchange fee. Contact Customer Sevice via their Service Form https://eurail.zendesk.com/hc/en-001

Exchanges are not possible on  passes sold in most discount sales, also the above only applies to passes where travel has not commenced.

First you need to check if your passes are exchangeable. This you see in the conditions of purchase that you find on the invoice that you got in your confirmation email. You can also find the invoice in the order overview in your Interrail account.

If the passes are exchangeable you need to first make sure that the old passes are deactivated. Then you buy the new passes and send both the old and the new pass numbers to Customer Support. You will then get a refund of the price of the old passes less 15 EUR per pass. If you bought PLUS you get a refund of the full amount. 

Please read the exact details here.

https://www.interrail.eu/en/interrail-passes/ordering-info/refund-exchange-policy

Just a question of terminology - you do not cancel your existing pass but, if already activated in the app, you deactivate it before any travel. The new and old pass numbers are then sent for your refund. (This is of course subject to the above point on what the refund T&Cs are.)

Hi,

Thanks for the quick reply. This is the first time I'm using this and I'm still very confused.