Bring the phone into your carrier and ask them to check it out - it sounds like an echo suppressor problem, and that's part of their equipment. ("Breaking up" doesn't happen in digital communications, you "go digital" - either sound like you're underwater or like you're super autotuned, depending on the carrier. Breaking up would be somewhere the signal is analog and, aside from your mike and a few components on your motherboard, that would be in your carrier's equipment.)