How can a Pro Sites user update their PayPal account?

Hello, if a user wishes to use a different PayPal account than the one used for their current ProSite account, how can this be achieved? I have 2 users which accounts expire soon and they would like to re-subscribe via a different PayPal account.

I tried to cancel the account and re-subscribe to the same account (same sub-domain) but the error pops up "Sorry, that site already exists!".

Thanks.