Have anyone found an authorized Iphone 4s / ios 7.1 wifi connection fix?

Since updating my daughters iphone 4s to the latest version of ios 7.1 we have not been able to connect to wifi or bluetooth. Also the phone is extremely slow in the network menu.

I don't want to heat or put the phone in the freezer to solve it, and is looking forward to see an authorized fix.........

Have anyone found something useful?

I've already tried all types of reset / reinstall etc..

Apple - your acknowledge of the problem would be appreciated. Need urgently an authorized solution!!