Paper trail
The paperwork trail will ultimately exonerate or lack of will crucify him.
If he has records of sending via some form of recorded delivery, or acknowledged email, an invoice for the service, a statement, a reminder, a 7 day letter and a final notice then he's covered.
If however he has seen red when they have terminated him, and he's shut down the service in spite, it's unlikely the judge will take his side.
Always do things in writing, never by phone.
Biting the hand that feeds IT
