(Nature?) Thank you for buying my lesson. But the time of lesson is hard for me, because in my time zone is 4:00am. If it will be a problem to you, it is be fine to refund. Sorry and It is a pity that our time is not match
(How to reject politely？） 这个在 英语 (英国) 里怎么说？

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Thank you for purchasing my lesson. Unfortunately, I regret to inform you that due to the difference in time zones, it would be impossible for me to conduct the lesson at the requested time slot.

I will arrange a refund for you. I sincerely apologize for any inconvenience caused. If you have any further inquiries, please feel free to contact me.