Hi Shien, it's inside BBM iPhone app. Press the vertical three points at the right corner on on the menu below next to 'Groups'. Go to 'Settings' where you'll find a button 'Report a Problem' there below your email address paste your INC number and press 'Upload to Blackberry Support' Hope it helps.
I solved my issue by signing in on another iphone and then signed back into my iphone. I lost d chat history but my pin was intact and my contacts re now ok. I hope it stays ok. Will update you when issue occurs again