Dear Shuang

I am sorry that you double booked. Unfortunately, since you are only informing us about this afterwards, we have already paid the providers of the excursions for your participation. Similarly, if you had informed us before the conference about your travel arrangements, we might have been able to cancel the babysitting service for the last day, but at this time, we are obliged to pay the babysitter. 

I trust you understand that because DRUID is a non-profit academic organisation with extremely limited funds, we cannot refund you for costs that we cannot recoup.

Kind regards