Mullinsky said:
I get it, so the benefit is that you could get a really good phone form one company and then use a cheaper provider to make phone calls. What about hacking the phones to get free calling.
As far as GSM goes....
No that can't be done, the operator has a record of your IMSI (International Mobile Subscriber Identity) (see _http://www.pt.com/products/gsmintro.html for details) and IMEI (_http://www.gsm-security.net/faq/imei-international-mobile-equipment-identity-gsm.shtml) so can identify you, so can charge you appropraitely. IMEI is on your sim, so you can remove taht and try and make a phone call, you'll note you can only make emergency calls... In thoery you might clone a phone with someones IMSI/IMEI details however manufacturers go out of their way to stop you doing this and there are many security features on both the phone and network side to cross, that's not to say it can't be done. Read here _http://www.totse.com/en/phreak/cellular_phones/thehackersguid179191.html and here _http://www.isaac.cs.berkeley.edu/isaac/gsm-faq.html
Mullinsky said:
I assume this would be much like internet hacking, which is not really possible because you need the service sent to you? What else can do done to them?
you could put them in a pint of beer, that's always good for a laugh
Mullinsky said:
Can North American cell phones be opened and used in the UK and vice versa, or do they run on different frequencies?
yes and no.
US uses GSM 1900MHz and to a less extent GSM 850MHz.
UK uses GSM 1800MHz (Orange and T-mobile) and 900MHz (O2 and Vodaphone)
If you have a dual band phone in UK it will be 1800/900 for EU use.
If you have a dual band phone in US it will be 1900/850 for US use.
If you have a tri band phone in UK it will be 1900/1800/900 for EU/US use.
If you have a tri band phone in US it will be 1900/1800/850 for EU/US use. (or could be 1900/900/850).
I guess there are some quad band phones out there which run 1900/1800/900/850Mhz which would be as flexible as you could get - (concerning GSM only)...
So it depends on what phone you have to start with before you unlock-it as to whether it would work in EU/US.
-cts