BB Curve 8900 :: Heartbeat Sound While On Phone

This is my first post on the forums, but I do think I'm a fairly knowledgable BB user. Had 3 BBs over the course of a few years, so I can usually rectify small problems as they arise. However I've recently come across something that I am not sure how to solve, or maybe it is not fixable- I do not know.Basically my phone has been making a constant heartbeat sound when I make or receive calls. Doesn't matter if it is on speakerphone, or the normal phone. Its also not just a slightly annoying noise in the background, it cuts off the person on the other end and breaks up their speech. Essentially kills any phone conversation because I cannot understand the other person. I am not sure if the other person can hear me or not. This has been going on for about 3 days now, and is very irritating.I would like to find a way to fix it rather than get a new one. My old pearl's trackball died, so I had to get a new phone, which led me to the 8900. The keyboard on that quit working, so I got a new 8900, which was luckily just under the one year warranty. Now this one is having this problem, but its just a few weeks outside the stupid 3 month warranty on replacements. I'm fed up with ATT and BB because of these device failures, and also because ATT never provided me with my $100 rebate, even after complaining to corporate.It's just a situation where I feel robbed in a way, and just want to find a way to get my current phone to work thru the rest of my contract so I can upgrade to a better device.Any suggestions of how to rid myself of the heartbeat noise? I'd really appreciate it.