My iphone 4s is also having odd connectivity issues with my 2013 Mercedes. Sometimes it will work with a call.. and other times it will not. If connected to a call - upon the call's end, it does not go back to the radio - which it did when i first got the car. Also - sometimes the system cannot find the phone.
Should i call Apple directly to alert them? After some research i have found that this is happening in MANY other cars (vokswagen, acura, etc.) and Mercedes told me they have only received these concerns with Apple products.
Since this is not a car issue - i will need to contact Apple. Maybe find out when a software update is available(???).