There is no call center. You can make a request via this form: 

Submit a request – Eurail Knowledge Base

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

It depends on the terms of your purchase, some discounted passes have no refund as part of their conditions, refer to your order documents to clarify.

There is no phone support.

The refund condition for your pass should be in your confirmation email and also on the invoice that should be in your Eurail account under "Order Overview". Most likely your pass is refundable for a fee of 15%. If you bought Plus there is no fee. 

Here is the detailed information about refunds.

https://www.eurail.com/en/eurail-passes/ordering-info/refund-exchange-policy

Your second question I don't understand fully. Who do you want to call? There is no phone number to Customer Support.