The internet connection on the ship is via a satellite uplink. There is no way to get any kind of internet service on board other than to sign up for the NCL program that they offer.
Consider visiting an internet cafe or internet shop once you get into a port. The internet cafes/shops are growing in poplularity and prices are very CHEAP. You will see many of the ships crews in the internet shops, writing home to family members. In fact, some the port internet shops are so busy, you may have to stand in line to get in especially when more than one ship is in the same port.
If you sign up for the ships internet service, you may find on sea days, it is very slow and difficult to even get on line. The NCL ships have routers stategically placed in hallways near staterooms for wireless, but at times the upload, download rates are extremely slow, and you can eat up air time very fast.