Thanks for the question. I understand you are experiencing issues with the touchscreen of your iPhone 4S. The following article will help to troubleshoot this issue:
If your device is experiencing any of the symptoms listed above, try the following steps:
1. Restart your device
- Hold the On/Off button until "slide to power off" appears. Slide to power off your device. When it is off, press the On/Off button to turn it back on.
- If you can't restart your device, reset it by pressing and holding the Sleep/Wake button and the Home button at the same time for a least ten seconds, until the Apple logo appears.
2. Clean the screen with a soft, slightly damp, lint-free cloth.
3. Avoid using the device while wearing gloves, with wet hands, or immediately after applying hand lotion.
4. If you have a protective case, or if you are using a plastic sheet or film on the display, try removing them and testing the device without it.
If the steps above don't resolve your issue, please schedule a service appointment with an Apple Retail Store for evaluation. If an Apple Retail store is not an option, contact Apple to find out your best service option or see the Service FAQ for your product.