Uninstallation of old version is not happening automatically

[PWLibrary]

I'm using Installshield2020; 
 I'm trying to upgrade my old version of product.
When i try to upgrade, i get an error "Another version of this product is already installed.Installation of this version cannot continue. To configure or remove the existing version of this product, use Add/Remove programs from Control panel"

Expectation is old product should be uninstalled automatically and new version should be installed.

If i try to change product code, both versions are coexisting. How to resolve this ?

[varul]

You need to create a major upgrade entry in order to uninstall older version, Please follow the steps mentioned in below KB article

https://community.flexera.com/t5/InstallShield-Knowledge-Base/How-to-Configure-a-Major-Upgrade/ta-p/193052

https://community.flexera.com/t5/InstallShield-Knowledge-Base/Create-a-Major-Upgrade/ta-p/3879