AFAIK, one can upgrade at anytime, even if you are still within your contract period. All that will happen is that the day you upgrade, a new two year contract period kicks in. I've done it last year to "score" a free upgrade from 2 to 4 Mbps. (The price was the same). Only once the contract expires one can elect to go to a package of a lower VALUE. You effectively need to cancel the old, and apply for the new.