You can request a refund from this page - https://railway.app/account/billing

Click on the refund button besides the latest invoice.

I tried it but got an error

Then i'm sorry but you would not be eligible for a refund.

Ah, so how should users try the railway service to determine whether it is suitable for them?

That would be the trial plan.
It's listed in the docs that regions are only available on the Pro plan - https://docs.railway.app/reference/regions

But I understand that may not be super visible, so hopefully Railway can implement a clear a concise table of the plans and what features the plans get.

Why don't I see this from the plan comparison，I didn't read the documentation first

https://railway.app/account/plans

Yeah strange regions are mentioned in the Pro card.

So I can’t apply for a refund?

As per that message you would not be eligible for a refund unfortunately.

According to the services of other paas vendors I use, the region can be switched at will, so when I changed to railway, I defaulted to the fact that it can switch the region, but it is a pity.

That's a fair assumption but at this time regions can only be offered on the Pro plan.