ITunes Sandbox account credentials are requested continuously


I am trying to implement IAP in my application but now it asks for sandbox account continuously. I tried removing that account from sandbox testers, but result is same.I removed all IAP related codes,but result is still same.I downloaded my app from store(that has no IAP implementation), even it still asks for credentials. I am going crazy with it. I also tried hard reboot and removing transactions in all cases but it does not help too.

Remove the sandbox account from your iPhones settings and if logged into game centre with that account, remove it from there as well.