A hold is a named object in a student system. The person who lifts it searches on your ID, not on your narrative.
Give them the key
Full name, student ID, the hold exactly as the portal spells it, the term you are trying to register for. Then: what clears this, and is there a form I already missed?
A cold reader in a registrar's office reads fifty of these. Yours should look like the ones they can close.
Leave the assistant's theory out
"This hold is illegal" is not a question they can file. "What document clears BURSAR-HOLD" is.
Send it as mail
They are not on RelayLink and do not need to be. You still get a thread with the answer, which is what you will need if the hold reappears next term.
If two offices are involved, ask the registrar which one. Do not send the same letter to both and hope.