IPhone 4 continues to display "this accessory is not compatible with this device" I only got my phone a week ago and I have only plugged a charger into it... Any ideas on how to fix? Ask your question.

Phone is and has continued to display "this accessory is not optimized on this I phone... It flashes on the screen continuously even when phone is locked, wasting battery life in the process. I could understand if I had used a dodgy charger but I have only used the charger I got with my iPhone. And it has been happening since the first time I charged it. Also the keyboard sounds go on and off when I'm typing, any ideas. Cheers.