"Modem" -- cable modem? Are you accessing netflix via your computer? or dedicated routing device? You say "majority of the time," meaning you actually connect a minority of the time? Your description is weak, but would indicate you need to call tech support at netflix and not rely upon pot-shot guesses from random individuals from the cloud.

As far as your refund goes, you are out of luck. It isn't Netflix' problem on how you receive the signal... that is entirely up to the user.
First of all if you don't have a smart TV.. how were you connecting to Netflix??? were you hard wired to the modem?? Do you have a Roku device or a Wii to get the wireless signal??? The only thing I can suggest is if you are depending on a wireless signal through a second party wireless device as mentioned above. Try raising the modem higher like to a window sill or even a shelf... electronic devices that are constantly on, tend to get hot and their internal components aren't the same as when they were new. If you are hard wired to the modem, try cleaning the contacts where the cat 5 cable connects on the modem... and or replace the cable.
I honestly don't know how you are receiving your signal to your TV since you didn't mention it.

Is your wireless also assessable by a computer. check your speed at speedtest or speakeasy. We've had trouble and found the modem was slow and it was reset and fixed it. I also had to have my provider reset the connection a week ago, the problem was on their end!