Too bad you're having bad luck - my friend and I have had great results with the same Packtalk Bold unit you have. Fidelity is so good that if we call each other at home, we never realize we're being called over the Cardo. On bike trips, we rarely have issues, typically only if on twisty roads and far apart, or if the battery is low. I've spoken with Cardo tech support over the years and they've been very helpful and patient. Certainly, one secret is to keep the Cardo updated to the latest firmware and phone software.
Unfortunately that has been my experience, the units not working as they should is one thing, the point is more the bad customer service. My point is that if you do have an issue, it might not get resolved by them.
