It might be more serious than you realise. It appears GIO cancelled your policy. You are usually asked on a proposal whether you have ever had a policy cancelled. If you answer yes, alarms go off and the insurer often doesn't want you, which might amount to having a proposal declined, which is another question you are often asked, so now you're a two time loser and doubly unattractive. Failure to disclose a cancellation may be grounds for an insurer to cancel a policy or avoid liability on a claim.
Under Section 75 of the Insurance Contracts Act http://www.austlii.edu.au/au/legis/c...84220/s75.html
the insurer is required to give you a written statement of the reasons for cancellation if you request it in writing, although no time limit is specified, so write to GIO:
" Pursuant to S.75 of the Insurance Contracts Act, I require a statement of reasons for cancellation of my policy number ........
I also require an explanation of the reasons for cancellation after I was specifically advised by you several weeks beforehand that the modifications to my car were acceptable. I require this information within 14 days of the date of this letter. I draw your attention to the substantial fine which can be imposed on you if you fail to provide the reasons for cancellation."
The aim of the exercise is to get the insurer to reverse the cancellation decision, which might require IEC's involvement, so that you have a clear insurance record for the future.