I'm certainly no expert on this, but it is a common issue apparently. I've never had the problem.....
I would reccomend reading throught this thread....
http://www.blackberryforums.com/show...=dropped+calls
If you decide that you need to downgrade the OS, the link is here.....
http://www.blackberryforums.com/show...=downgrade+3.8
I am NOT reccomending this....I am just providing the information I have seen on here before.....
Unfortunately, I'm off to a meeting. sorry I couldn't be more help!
Good Luck.