Changing Font Size on Poly VVX450

We recently moved and had new phones installed at our new location. The font is very small and difficult to read, and I need to be able to quickly read the phone number to accurately take notes while listening to our customers. I've googled how to increase the font size on the Poly VVX450, but this option is missing from our settings and I am thinking it may be restricted by Comcast. Is there a way to increase the font on these phones??