my iPhone 4S often crash and have a GRAY wifi after iOS 6.1.1

Hello there. I knew that many people have GRAY wifi after updating to iOS 6.

but is it just the wifi that become you guys' problem? because beside gray wifi, my iphone often crash with some app...

I must restart about 1 times in a week. this problem appears after I upgrade to iOS 6.1.2..

there's no problem in 6.1.1 though 😟 in the beginning (with 6.1.2) I can turn on the wifi but the connection is REALLY BAD.

so I was trying to reset all network. but then the wifi become gray until now 😢

I already updating to 6.1.3 and there's no change. there's still crash and gray wifi 😟

I tried to reset network, restore without having backup and soft resetting and they didn't help at all.

is there a way to downgrade my iphone? or the only way is to change it to the new one?

because my 4S is just 6 months old, I still have my guarantee.

please help! thankyou 🙂