Hello!
Not sure what you mean by an Android 4?
Do you live in a poor signal area? Do you get missed calls, calls dropping etc? In a lot of cases, this can be fixed by switching to 2G only networks when you're getting bad reception.
You could try that, or if you want to give us a little more info, that would be appreciated (we'd probably be in a better position to assist).
If you want to give us more info, you'll either need to post again, or create an account.