You will need to cancel your previously purchased pass to purchase a promotional pass. Unless of course you want to use them both.

Check the interrail website, in your account, whether you can cancel your previously purchased pass, and at what price.

Thank you so much for replying! But at the website it says you can get the refund for %85 and it might take a week or two. Although the offer ends in 2 days. But I will still try it

That is a choice you have to make yourself, whether you are willing to cancel the pass and get 85 percent of the total amount paid back.

Good luck!

Of course you should not wait to buy the new pass until you have received the money back from your old pass.

EXPect to have to wait for 2-3 month for the refund money to come true. This is not the very 1st thing they will go after in busy times.

Is the 15€ exchange fee not an option? Is cancelling the previous pass the only possibility?

I’m not sure but I also tweeted the interrail official page, they told me I can refund regarding my tickets, and then re-purchase a new ticket with the %50 promotion. Since they said re-purchase, I don’t think its possible for an exchange. But, after I requested for a refund they said the refund should take 2 business days to complete so  maybe it’s not that big of a deal. I recommend you refund and buy one again because that’s just what I did.

Hope I was helpful.

Exchange for 15€ is certainly an option. The only thing is that you have to request that via customer service.