my iPhone won't let me change my lock screen

You could try resetting all settings in Settings>General>Reset>Reset all settings. The phone will reboot on its own and then you should be back at the default home screen. All of the default settings will return and you will have to enter all of your settings again, and that includes all WiFi network passwords. It can take some time to do this, so just be forewarned. You will not lose any data when you do this.

I am having the same problem and I went to this website where I could talk to these people who work with apple but every time I asked them what to do they would talk to me for a second and then the page would close and say "we're sorry please try again another time" so I'm honestly not sure what to do

I assume that you mean one of two things. You are not able to change the passcode to unlock the iPhone or you can not change the wallpaper. If my assumption is correct, describe what happens when you try to change the passcode or wallpaper. Provide as much detail as you can, please.

Try closing the Settings App and force restart your phone. No data is lost when you do this.

Press the Home button two times quickly. You'll see small previews of your recently used apps. Swipe left to find the app you want to close. Swipe up on the app's preview to close it

To force restart your device, press and hold both the Sleep/Wake and Home buttons for at least ten seconds, until you see the Apple logo.

I closest my apps and I also reset my phone but it still won't change munch lock screen saver. Anything else i can do or should I take it to the Apple Store?