DTDC Courier & Cargo — parcel not delivered not returned yet

I had sent 2 parcel by consignment number n98116160 from ratnagiri to dubai on 2nd december 2017 by express delivery service. As promised by courier agency the parcel was supposed to reach dubai on 6th or 7th dec 17. Its contained brochures & stationery material for exhibition at dubai from 7th to 9th dec17. I reached dubai on 7th & was there till 9th in dubai but didn't received the parcel. Then 9th evening the event organisers received a call that parcel is come for delivery but they denied to receive it as the event was over. Now i am asking the agency to return me my courier parcel back & my paid courier charges back as they were not able to deliver the parcel in time or given date. But the agency is asking me to pay extra charges to get the parcels back. Was it my mistake that the courier not delivered in given date? Was it my mistake that we paid heavy charges for express delivery?
Please refund me my paid courier charges & return me my parcel