Contract Cancellation

Hello everyone,
I need help. In March, I moved to my flat place for three months. Since I've written to the owner, I wrote a letter to O2 explaining that I was leaving the country and that I wanted a cancellation of the contract. Since, I have not received the router and left. In July, when I returned, my landlord sent a letter from O2, the letter said O2 could not respond to it because it was written in English. Again, I looked for a friend who wrote a letter to O2 in English, and explained the whole situation, but now I have received contradictory responses. One on my email saying that I should send the registration of my residence to O2 and another letter saying that the contract can only be canceled in December.
I have asked for more than two letters. By the end of this month, I am moving to my country, and I am not coming back; therefore I want to cancel my bank account. If there is anyone who can help with this, please, I would be happy.