3G Connection Don’t Work in Apple iPhone 4S

I just bought iPhones 4 and my 3G connection doesn't work! I've researched the problem and *I think* it might be a drivers problem. Does anyone know where I could find the drivers for iPhones SIM card slot?
Or am I wrong and the issue is somewhere else? I can't call Apple's customer service, because I'm from Ghana.
Thank you.
