I am an "original" FIOS customer, having signed up for the service from the moment it came to my neighborhood 5+ years ago. We initially rented two DVR boxes because the multi-room capability at that time would not work with HD. Once HD multi-room became available, we exchanged our two DVRs for a single multi-room HD DVR and and an HD settop box. We discovered that Verizon did not update our account information accordingly and has been billing us since April 2010 for two DVRs. Various past calls to Verizon have yielded no resolution and it was not until we got very aggressive in November 2013 that our account was updated. I can't tell you how many times I was told someone would call me back and never did!
Now that this has finally been resolved, Verizon is refusing to give me a credit for the overbilling beyond the previous 12 months (there are 40 total months in which I was overbilled). Verizon's records are spotty relative to all my past effort to get this resolved, but they do concede they have records of my calling in February of this year. The fact that ten months have passed since then and they won't even take responsibility for that delay is ridiculous and unacceptable.
I can't speak for everywhere, but the statute of limitations in my state (Pennsylvania) is 4 years for contract-related actions. Verizon is in no position to claim they will only credit back 12 months of overcharging when it is the party at fault. If I do not get satisfaction on this matter shortly, that will be the next step.