How to change a subscription's login info in Plesk?
When you look at the top right corner you can see the active subscription under "Logged in as ***". To change the subscription's login info, follow the below steps.
Go to Websites & Domains tab.
Under Websites & Domains tab click on the Web Host Settings icon.
A form similar to the below image will appear, specify the required details in that form.
Click OK to complete.