I wasnt to buy three used cellular phones in the USA to take to
Africa. Do all cellular phones in the USA work on the simcard system?
If so, if I buy cellphones here can I remove the used simcards so that
the service providers in Africa can merely insert their own? I know
that the cellphones in Africa all have simcards provided by the
service provider one signs up with.

Hey janiceashby,

In order to use a GSM(sim card phone) enabled phone, it would need to
be unlocked from the provider. For example when you buy a Nokia phone
on a plan from AT&T or T-Mobile it is locked to that company, so what
happens is when you put in a sim card from an African company(i.e
Vodacom) it will give you a sim card error. Now there are many ways in
which you can have your used gsm enabled cell phone unlocked,
software-wise and hardware-wise. You can also buy some used GSM
enabled cell phones already unlocked on ebay. The nokia gsm phones are
the easiest to unlock and are the easiest to come by. That being said
not ALL cell phone providers lock their phones, but 99% of the time
they are. I am in Canada and I have bought several cell phones from
the US and unlocked them to use here on the GSM network in Canada. To
summarize my answer for you in short, Yes you can bring almost any gsm
phone to Africa and use it on their netowork, however it must be
unlocked.

Locking is normally done only by service providers in certain
countries. For e.g. some asian countries on GSM like India/Singapore,
don't lock their phones to certain SIM, which implies, you may you buy
a GSM phone from Singapore and use it in India and vice-versa.

So you may need to look out for phones which are not locked, and I am
pretty sure that might work in Africa too. Don't go into the hassle of
unlocking phones as you may spoil them inadvertently

As far as I'm concerned, most part of Africa uses the european GSM,
which is not compatible with the american system.
You will have to buy an unlocked phone to use it there, so that the
phone can recognize whatever company signal is there.

Not true. The gsm phone systems in the US, Europe, Africa and anywhere
else in the world *ARE* compatible. They merely use different
frequency bands. Not all phones can operate in all frequency bands
though.

The frequency bands are at 850 Mhz, 900 MHz, 1800 MHz and 1900 MHz.
Many gsm cell phones nowadays are Triple Band phones, which usually
cover 900 MHz, 1800 MHz and 1900 MHz. Those phones can be used in the
US, Europe, South Africa and many other countries. So make sure you
get one of those.

In rare cases, 850 Mhz are used. There are also Quad Band phones which
work everywhere. You didn't mention which country in Africa you are
visiting. Check out the following page. It lists the frequency bands
of many countries. I hope the African country you're visiting is
amongst them:

http://www.thetravelinsider.info/roadwarriorcontent/quadbandphones.htm

Also, take a look here to get some basic gsm infos: 

http://www.planetomni.com/FAQ_gsm.shtml

As others already said, make sure the phone is not provider-locked.
Unlocking tools are available on the internet for many phone types
(E.g. Nokia, Siemens). There is a minimal of screwing up your phone. I
wouldn't be too afraid of it. It's fun (and probably illegal :-D ).