The field that you have to change is the Bundle Display Name (CFBundleDisplayName is the raw key name) in the info.plist file from ${PRODUCT_NAME} to ‘your desired name’.
Note: CFBundleDisplayName is different from CFBundleName. CFBundleDisplayName is the human visible/marketing name displayed on the device home screen, under the icon etc. While CFBundleName is the filename of the IPA and the folder for the app on the file system, ‘Whatever’ for example would be archived as Whatever.ipa and the app would be installed on a device under the folder called Whatever.app.