Not before the last 30 days. Your leverage to getting a deal is the belief that you will be prepared to leave. Phone before your last 30 days and you're in a weak position. Best bet is to arm yourself with knowledge of what competitors will offer you as a new customer, phone and offer your 30 days notice during those last 30 days, and see what they come up with.
If you're up for some serious brinksmanship, then order a different ISP for installation at the end of your VM contract, phone up and offer your 30 days, and wait and hope for an outbound retention call. But don't blame me if you miss that call, or it is never made.....
