In my phone I have changed the overwrite button on in speech mode. From that time I could not access my phone through my 6 digit password. Now with repeating passcodes phone is locked for 3 hrs. Kindly help me as soon as possible.

You will either have to wait or reset your phone. There is no way to bypass this.

If you forgot the passcode on your iPhone, or your iPhone is disabled or unavailable -

Click on the link for instructions on how to reset your passcode without a computer if you have iOS 15.2 or higher.

If you see an iPhone or iPad unavailable message or Security Lockout screen - Apple Support

Click on the link for instructions on how to reset your passcode using a computer.

If you forgot your iPhone passcode - Apple Support