Iphone connectivity
 

Hey guys i recently purchased my A Class and loving it !

I can connect my iphone to bluetooth and play music through it without a problem but i like to have it plugged in and charge at the same time!
So i got my iphone 4s and the cable and plugged it into the USB slot and it comes up with 'USB device unreadable' is there something else i needed to purchase with the car to make this work or maybe i just need a new cable?
If anyone has any idea it would be great thanks!