Yes, the ewallet can be deactivated, you will just need to follow these steps:
First, visit the Yakkyofy dashboard and click on the icon displayed at the upper right corner of the screen.
Then select Edit.
You will now display your personal account's page, on which you should click on the Settings tab.
If your ewallet is activated the option on the Settings tab will be displayed as follows:
In order to deactivate the ewallet, you will just need to click on the switch and the option will be deactivated as shown on this last image: