Eva B class tickets are non-endorsable and non-reroutable, but can be date changed (often with no charge) or refunded (for a fee). Refund only applies if ticket completely unused (eg, you can’t refund the return after flying the outbound leg). Normally loads of other restrictions relating to date, route etc, but that won’t worry you…

Be warned that it may take 90+ days to get a refund…

Amazingly cheap for a ticket with such a high degree of flexibility, to be honest!