i used to live in Belgium but now i am moving to USA, and my question is if my nokia n81 8GB (that i bought in Belgium) will work with a prepaid card from at&t?
No you can't use your Nokia N81 18gb mobile with AT&T sim until you unlock it from its present network provider ...You can easily unlock the phone using sites like Unlock-Zone.com here they are rendering network unlock code for all mobile models at reliable cost ...After purchasing the code from them visit sites like MobileUnlockGuide.com to get free instruction about how to use that code and unlock your phone ..After unlocking the phone you can freely use it with any GSM sim in any countries ...