Looking for Answers about Straight Talk Straight Talk Unlimited Minute/Unlimited Text Message/Unlimited Mobile Web Access/30-Day Service Card?

Minutes do not rollover.

Every 30 days (not monthly) you have to add time or if you run out of time before the 30 days you have to add time.

Absolutely, you can refill online. You can buy refill from Walmart.com online and they will email the PIN to you. Then you can dial 611* (send) to refill or go to Straight Talks webiste to activate the minutes (scroll to the bottom of their webpage)
https://www.straighttalk.com/Refill

There are several other options at the Straight Talk website, all required a credit/debit card:

You can 'refill on demand' using a credit card (no pin required).

You can setup a 'Reserve account' and buy as many refills as you like, use them on any Straight Talk phone you want to. You can use a Debit/credit card.

You can auto-refill (automatically charged to you debit/credit card every 30 days) and no PIN is required . With this option you get a free month after 13 consecutive billings, makes it even more affordable!

Visit the website:

https://www.straighttalk.com/Refill

No. And if you renew too early, you will lose money for unused days.

There are no roaming charges. It's unlimited nationwide. In the areas where there is no service, you won't be able to use your phone.

Straight Talk cards only work on Straight Talk phones.

No Skype is not available.

Straight Talk provides 'Mobil Web Access' only. All you can do is surf the WWW.

Streaming music, live radio, telephone calls, etc. all are not available. You also can't use the phone as a cell modem.

Walmart tends to have a limited selection of the latest model Straight Talk phones. The Straight Talk website always carries additional models. And if you buy from an Ebay.com seller you may find models that are older too. For info here's a list of Straight Talk phones, followed by a link to the most current lineup for your area (type in your zip code):

http://www.straighttalk.com/Phones

http://www.straighttalk.com/ShopPhones

You have to buy a Straight Talk phone. I don't know of any cell phone companies that let you use their phones on another carrier's line.

You have to buy straighttalk branded phones to use ST service.
The phones that have "c" after model number run on verizon network, the ones with "g" run on AT&T I believe. You might want to check coverage maps for your area to see which network will give you the best service.
And put your zipcode in at straighttalk website to make sure they cover your area. http://www.straighttalk.com/