How are you on the phone in the car?

Hi, everybody, I’ve been looking for a solution to phone in the car for a long time. 1. I bought an earplug from Logitec. Somehow it was always empty or it rang and I forgot to do it or whatever. sometime I used it more… 2. I bought a tomtom + handsfree device. went quite well until I couldn’t bear it as always jmd said: What? I understand you so badly. 3. I have an XDA with handsfree mode. D now I don’t understand people anymore Now that I finally drive a new car I should also find a solution for it or? I have the Sony MP3 radio in it. What do I have to buy, install etc. so that you understand me a) and b) I understand everything c) I don’t get away cheaply