Contract cancellation

Hi all,

I will be leaving the country at the end of September. I have DSL L package at home and I am looking to cancel it.

From my understanding I have to send a letter to the main office. However, one point I don't understand is that I have to return the router which I believe I was charged €50 for. Anyway returning isn't such a problem other than I can't return until I am moving out so my question is will it be sufficient to send the letter now and the modem later before we leave?

Thanks.