how can i get i immediately aprepaid phone card?

I'm "answering" the question rather than asking for a clarification in
order to get you this info as quickly as possible. However, if this
answer is not specifically what you are looking for, please let me
know and I will clarify/lengthen my answer.

AT&T offers prepaid phone calls purchasable online:
https://att.ecustomersupport.com/order.asp

You will get a card image on your screen that you can print out and
use as a card. (If you don't have a printer, you can just write down
the PIN and use it, cardless)

Alternately, there are many off-brand prepaid phone cards available:
http://www.phonecards-prepaid.com/store/tcproductlist.asp
These claim to be cheaper, though they also have much more fine print
(legal language) that would need to be scrutinized to search for extra
fees and restrictions.

Of course, online purchases require a credit card. If you don't have a
credit card, you will most likely need to go to a physical location
(7-11, for instance) to purchase a prepaid phone card.

You can find the closest 7-11 to you by using the location tool on
their site.
http://go.vicinity.com/7eleven/prxStart.dsp

Again, if you are looking for more information than this, please ask.

Walmart sells AT&T phone cards in varying increments (30, 60, 90, 120
or more minutes) for a pretty reasonable price per minute (not sure
what it is these days). I bought my 60 card for $6.00 (10c a minute),
but have refilled it numerous times by calling the 800 number and
charging the refill to my credit card. During that time, the price per
minute has dropped a couple of times (I presume because I'm a repeat
customer using the same physical card over and over, which lowers
their physical production and distribution costs) and I can now add
additional minutes for 6c a minute.

Wal-Marts are pretty much everywhere in the U.S. If that is where you
are located, you can find the nearest Wal-Mart by entering your zip
code at http://www.walmart.com/cservice/ca_storefinder.gsp?NavMode=7.

Hope this is a help to you!

P.S. If you don't have a credit card, you can recharge these phone
cards by taking them into a Wal-Mart and paying cash. Pretty handy.