You can avoid the single supplement by agreeing to share a twin room.

你如果同意与人共住双人房就可免交单间附加费。

What's the rate for a twin room?

双人房费率是多少？

I'd like a twin room with a bath.

请给我一间有浴室的双人房。

Would you mind a twin room instead?

您介意要两张单人床的房间吗？ ？

Would you mind a twin room instead?

您介意要两张单人床的房间吗？