[gmbouah]

I bought a 2nd-hand unlocked AT&T BB 8820 OS 4.2 from the USA. It works fine on my local South African GSM-networks but as soon as I update it to OS 4.5 I am unable to make calls or access BIS. It just displays the message 'no service'.

Please help.

[Dubdub]

Resend the service books (see the FAQ) and do a battery pull.

If that doesn't work, call your cell carrier.

[tsac]

Also check to see if it really is unlocked.

How do I determine if my BlackBerry is "unlocked"? - BlackBerryFAQ