Update or delete payee's adhoc bank account

A payee for an adhoc payment was created, and the payee's bank account wasn't populated with the BIC Code.
Once it's saved, we can't update it to put the BIC Code in it, it's greyed out. (see screenshot).

Is there a way to update it after the creation (via the screen, or REST API - I tried, and had the following error : The value of the attribute BIC is not valid ) ?

And if it's not doable, is there a way to delete it - due to GDPR concern