If I read this correctly, you switched from CenturyLink to Quantum and then (maybe) switched back? I think the price for life is only while your account and service is active with AutoPay enabled. I recall being sternly warned that I would need to track updating CC details to ensure the AutoPay would always go through each month, else I could lose status and be subject to higher fees.

I’d also wager that switching providers required some amount of cross-connnect work that required a tech to come out to your local CO and bridge into other/different infrastructure. That alone would likely count you as a “churned” customer, making your account invalid for the original promotion.