Back to the problem at hand...........
Aon is an insurance agent, not a company. Neither want to hear from an Insurance Commissioner (your domicile state).
In written form advise them that unless the matter is handled per your "many" notices to them (not renewed) you will be forced to contact your Commissioner and the Company in which they renewed your coverage.
Further, you want to hear from them (in writing) in __ days. I've always found that a "return receipt request/proof of receipt" gets their attention when using the US mail.
Hal & Ginny Miller '04 Beaver Santiam PRT40
'04 Saturn Vue - US Gear Brake - Blue Ox tow
4 "girls" (3 Irish Setters - Retriever)