How do i change or remove a signature in docusign after its been completely executed?

@LauraKirk The envelope likely had an Advanced Option enabled that allowed Recipients to “re-assign” the envelope to another individual.  This can be disabled before you send an envelope but the envelope being completed there is really nothing that can be done for that envelope except to send a new envelope.  

The advanced option you want to disable is called “Recipients can change signing responsibility or assign a delegate”.

No changes can be made to a fully executed or fully completed envelope meaning all Recipients have taken action.  You would need to copy the original, make the appropriate adjustments to the Recipients and settings (Advanced Options) and send the new envelope.