How would I go about becoming an authorized AT&T and T-MOBILE cell
phone phone and service seller? I would need a list all requirements
and contact phone numbers needed to start the process. I have no prior
experience selling these.

The easiest way to become an authorized wireless dealer would be to
buy into a franchise store that already has pre-existing contracts
with various carriers.  In todays wireless market you will need to
offer more than just 1 carrier choice.  Some franchise stores require
investments upwards of $100,000 USD.
A good example of a wireless franchise opportunity:

http://www.bison1.com/showcase/atwireless.html
@Wireless 
50 Methodist Hill Drive, Suite 1500 
Rochester, NY 14623 
Phone: 1-800-613-2355 ext. 226 or 716-359-3390 ext. 226 
Web: www.shopatwireless.com 
Investment Range $US: 
$75,000 - $110,000 estimated total investment $25,000 liquid capital
Cellular services from carriers such AT&T, VoiceStream and Verizon
Wireless.
PCS Services from AT&T Wireless PCS.
High-tech toys like Palm Pilots and GPS.
Specialized mobile radio from Nextel. Satellite television service
from Dish Network and Direct TV.
Wireless data products that will put you in the forefront of the
wireless boom. Unique products such as the FRS (Family Radio
Frequency) products from Motorola.
Products from top name companies such as Nokia, Motorola, Ericsson,
Audiovox ect

Another wireless franchise opportunity:
http://www.wirelesstoyz.com/franchise_info.html
You can download the .pdf business plan and apply for a franchise
store online on the above page.

I also did a search on http://www.franchisegator.com and found 2
consulting firms that can help you get a franchise loan and make all
then necessary paperwork easier to deal with.
http://www.franchisegator.com/cgi-bin/profile.php?key=134&f_type=8
First, we'll help you determine what size franchise investment is
right for you. Once the approximate loan amount necessary is decided,
we will head into the financing stage. Upon completion of a thorough
personal financial analysis, consisting of detailed financial and
background information, you will have the opportunity to work with
Diamond Financial Services and other preferred SBA lenders to get you
on your way.

Here is another less-costly firm that will help you with your loans.
http://www.franchisegator.com/cgi-bin/profile.php?key=124&f_type=8
FranChoice provides a free service to qualified individuals in the
United States looking for franchise business opportunities to own. Our
consultation process will save you both time and money in your search,
provide you with intelligent choices based on your goals and
preferences and, best of all, it's free.

Hope this helps.
<-J

Digging a little deeper...i noticed that @Wireless franchise stores
also have agreements with T-Mobile.

https://www.shopatwireless.com/store/f_info.asp
About the Company
@Wireless® Enterprises Inc. (formerly Cellular Unlimited) was founded
in 1994, as a wireless agent in the Northeastern US. The Company
represented Bell Atlantic Mobile products and services. @Wireless® has
quickly grown to 62 retail locations, both Company owned and
independently operated.

We currently have agency agreements in place with a number of carriers
such as: AT&T Wireless, Cingular Wireless, Nextel, Sprint PCS, SunCom,
Verizon Wireless and T-Mobile. These affiliations allow our
franchisees the opportunity to satisfy a vast array of customer needs.
The company presently has the ability to provide wireless
communication in 42 states.

Could a researcher please set this question to "answered".  I expect
nothing in return, i simply answered it for fun.
:)
<-J
(it would be really cool if you would be willing to post a $5 question
on my behalf though)