If you use cash as a deposit, as soon as you balance hits zero, your sign and sail cards will no longer work and you would have to go to the pursers desk and add funds to your account. I'm not sure if they will give you notice upon the balance reaching some "low" point limit. Cash Is and option, but it seems like such a pain in the backside. Its much easier to use the credit card (current topic not withstanding) and pay it off before you leave the ship. But NEVER use a debit card (unless you have a huge checking balance) and have notified your bank that you will be doing so. Several banks will put daily limits on debit transactions and you may run into problems with that too.
jacquelinec -- you asked, "How do they notify me?"...
According to Carnival's website's Frequently Asked Questions concerning cash deposits: "As a guest approaches the deposit limit, the Information Desk will notify the guest that additional money must be deposited."
I read somewhere that the notification will be in your cabin or on your TV. Of course, if you haven't been back to your cabin, your Sail&Sign card will just stop working, as Jim C. mentioned, at which time you go to the Information Desk and cough-up more cash.
About credit cards, Carnival's website states, "A hold will be placed on the credit card at the beginning of the cruise...." "The hold will be released and actual charges will be billed at the end of the cruise."
The hold on the credit card I used has yet to be released. (I'm hearing the theme song to Double Jeopardy in my head.) And final charges cleared on Sept.10. In time, all will be resolved. It's just one of those things. I'll be better prepared next time.
This exact same thing has happened to me. Carnival also gave me a reference number and also acknowledged this is a problem with their system. 72-hours? Now way! They have had the charges on my account for 8 to 10 days now. It irks me because WHAT IF I needed this money? They currently "owe" me $253. I think this is ridiculous. I wonder if this money will be off my card by the time I leave for another trip mid October? I wonder if my credit card company will charge me interest on "pending" charges?? I had been warned ahead of time of this happening from some frequent cruisers but gave Carnival my credit card anyway. Next time I will use a cash deposit.
Sorry about the problems you had with the hold authorizations, I used to deal with these exact problems when I worked in the accounting department at a credit union. The reason the holds aren't falling off when the actual charge comes through is because the dollar amounts do not match. Most credit card issuers have systems that release the holds automatically and if the holds are for small amounts, and not for the $433.53, they won't fall off until the legal processing time limits have passed for the merchant to submit official documentation.
It is always recommended that you do not use a debit card for hotel reservations, car rentals, etc for this exact reason.
Check with your bank or credit card company before you go to see what their policy is on releasing such holds. We would release them with a fax on company letterhead from the merchant saying it is okay to release.