Keyboard types wrong letter iPhone 7s

Try and Force restart your iPhone 7

Press and hold both the Volume Down button and the Sleep/Wake button at the same time. Continue to hold those buttons until the Apple logo appears, release both buttons. (DO NOT release Side Button when invited to Slide Power OFF). 

If the above does not help, then remove any screen protector and the case of your iPhone and see whether that helps. If it does not, then you may be experiencing a failing display / touchscreen. Have your iPhone examined at the Apple Store or at an Authorized Service Center for further diagnosis and a resolution.

Axel F.

Unfortunately, the fix is probably not going to be all that simple. The screen likely needs to be replaced. About $170 at the Apple Store.

No. I meant the Volume Down Button and the Power button.

Axel F.