Actually, you have a supporting case in your favor now (especially, if you can prove the "upgrade" verbiage). If not that, the cruise line has a right to do what they did. However, since (and if) they consider it an upgrade, now you may request a real upgrade to any available cabin in the closest category up (since the actual new cabin is technically verse than your original).
PS. When we try to book a 3/4 berth cabin for 2 about, our cruise agent always warns us that a cruise line might move us to a different cabin in the same (or above) category at any time, if someone will try to book a cabin for 3/4 people, and none is available at the time of that booking attempt, and even a higher category cabin might actually be worse (location, configuration, a smaller balcony size, obstructed view like in your case, ...) than our booked cabin.