Why won't my iPhone 4s show incoming calls?

Having a little problem with my phone.
But first, a little detail. I have a Sprint iPhone 4s with iOS 7 (Beta 3). Everything else works fine on the phone.
I receive all text messages, notifications and such perfectly. But when it comes to calls, I sometimes get them, sometimes don't. This is especially a problem for my mother. She is threatening to take away my phone if I do not start answering her phone calls. The problem is… I don't even GET her phone calls. She thinks it has something to do with iOS 7, but I have no idea.

Any ideas to as why this is happening?

Hey probably it seems to be some internal issue. So better take it to the nearest Apple care they would get it fixed. Hope you find this useful.

I think you must go to check with the apple service center

Is your device's UDID registered? Many people have reported issues running the beta when they haven't registered their UDID on a site like http://www.instantudid.com/.It's $5 and I haven't had any issues on my 4S.

I have iOS 7 Beta 3 also. Sometimes it has some really strange glitches. What I did last night which seemed to fix most of the bugs was backing up and restoring the phone. Backup your phone to iTunes and then restore it by going Settings>General>Reset>Erase All Contents and Settings, then restore through iTunes. This should fix it, BUT I paid $6 to have my UDID registered, so I have 0 issue installing iOS7. If your UDID is not registered, I don't think you can just restore without a problem. Also, your glitches may be a result of not having a registered UDID because the server could be registering iOS 7 as foreign software, as it would do with a jailbreak.
And I see that some people are suggesting Apple. APPLE WILL NOT Help YOU. When you install iOS 7, it clearly states that you are installing it at your own risk. And Apple can't help you with Betas, for the Apple employees do not even have iOS betas on their support devices.

This is a bug in iOS7 betas. If you are not a developer, you should not even be using them anyways. My phone does the same, unless I have it sitting on the home screen all the time. If this is a major issue for you, google "How to downgrade to iOS6 from iOS7", and you can get it fixed quickly. Just a word of advice, stay away from betas unless you are a developer and need it or if you actually need that phone. It explicitly says on the apple site that betas are to be used on "development only" devices, and not ones that you actually need to use for everyday life.

I think it is software problem in your iPhone you can visit: www.mega-mobiles.de