No. My Voyage is free to use and does not require you to purchase an internet package.
To avoid roaming charges while at sea, please either turn off mobile data or switch your device to flight mode, then connect your device to the ship's Wi-Fi network (Cunard Guest Wi-Fi).
Once connected to the Wi-Fi, open your internet browser and visit "myvoyage.cunard.com" or scan the QR code on the guidance in your stateroom.