写一个电子邮件，告诉客户他们的订单已被取消。


订单编号：123456
客户姓名：张三
订单详情：一部手机和一批手机壳。
Subject: Order #123456 Cancelled 

Dear Zhang San,

I regret to inform you that your order with the details of one cellphone and a batch of phone cases has been cancelled due to unforeseen circumstances. Please accept our sincere apologies for any inconvenience this may have caused you.

If you have already made a payment, we will process a refund back to your account within the next few business days. If you have any further questions or concerns, please do not hesitate to contact our customer service team.

Thank you for your understanding and we hope to have the opportunity to serve you again in the future.

Best regards,

[Your Name]