Have just started to use my Iphone in the car and i have factory PTI, after making a call and then go to use the voice command function i get a loud feedback type howling noise, this has only just started since using iphone and never had a single problem with my Nokia previously. When i shut the car down and leave it for a while then start and see the phone connected i try voice command and all is fine it just happens after i have used the phone can anybody shed some light on the problem.

Thanks