Contract cancellation

My bill ends every month on the 17th so i went on december 17 to cancel the contract but the shop was closed on the 16, 17,18 and 19 i managed to cancel the contract on the 21 of december and i paid for january bill but 3 days from the new month wil not be paid because am traveling to egypt on the 22 of january and the bill will come out on february and the shop agent says that am going to pay one whole month subscription for these 3 days .. It is not fair to do so i wish to terminate it immediately cause i won't be able to pay the bill as i am out of town