Can i use my iPhone on a carnival cruise ship?

I will be taking a cruise on the carnival imagination next week, i would like to post pictures on facebook/instagram while on the cruise, but not sure how to cruise ships Wi-Fi would apply on my phone. Also i would need to be able to communicate with my mother (who is taking cruise with me) on the ship, but how would i do so without an internet connection/phone?

You have to either pay for Wi-Fi or for cellular service - neither of which is cheap. Wi-Fi especially, is spotty - save the pictures to post when you return from your cruise or post in port where you can find free Wi-Fi

As to communicating on board ship - get a pair of decent walkie talkies

Cell phone charges while underway are as high as 3 DOLLARS a MINUTE. ON TOP OF whatever you provider charges for international and roaming. Texting runs 50 cents to send, maybe 5 cents or free to receive, again, m depending on your carrier.

there's this quaint little ancient custom called writing notes on a post it that allows one to communicate.

Cruise ship cell phone and internet service is outrageously expensive. Use your phone as a camera. To communicate with mom, plan ahead and know where each other is going on the ship. Wear a watch and make arrangements to meet at specific times. You'll find that as big as the ships are, if you roam about, you'll likely be bumping into each other more than expected. Another option, determine a favorite gathering place (example: Serenity deck or aft Lido deck) and if you get separated, go there and wait, eventually they will find you or vice versa.

Unless one of you falls overboard, nobody will get lost.

Cell phone use is extremely expensive on a cruise ship. As others have suggested, wait until you get home to share your photos.

You don't need to have a phone to communicate with your mom. Go old school and do what people did before they had cell phones. Plan out your days and let each other know what you will be doing. Arrange to meet back at your stateroom at a specific time or meet each other at dinner time. If you are on different shore excursions, set a time and place to meet. You will have a phone in your stateroom on the ship (like a hotel phone system) where you can call and leave a message from other phones located on the ship.

Cellphones on a cruise are expensive, what I did on my last cruise was at ports if you go somewhere to eat or certain bars/cafes and on certain beaches if you rent chairs -- these places generally offer free Wi-Fi so connect to that and post on instagram and snapchat then. The Wi-Fi is free and it won't cost anything where as on the cruise it's super expensive and doesn't work very well either. As for keeping in contact I leave notes in my room (I took sticky notes with me for that) so if i went to my room and my parents weren't there I would write "not joining you for dinner today, going swimming instead, see you later" and then when they would go back they saw it and could leave another one for me if they wanted. Also, the cruise ship has phones on it that can call any room and that's free so use that if you want. Have fun!