iPhone contact search (with letters) doesn't return anything Suddenly my contact searching stopped working. If I write any letter (on search bar) in order to find out the specific contact(which I saved on phonebook with the same letter starting with) doesn't find the matching. [But, interesting thing is that, it's been working with only newly saved contact for some days.] 

it's important to tell that in order to solve that issue I synchronized my phone and also restored everyhting after backing up. Unfortunately, it doesn't help me.

Note: My phone is iPhone 4s and iOS 6.1.3.

Do you have any solution or advise fot that?
Thank you in advance.
It seems that you have multiple contact accounts on your iPhone. Open the Contacts app on your iPhone, tap on Groups and then tap "Show All Contacts". 

You can now view all of your iPhone contacts in one place.