According to CTX the screen resolutions for the monitor in question are:
1280 x 1024 @ 67Hz
1024 x 768 @ 89Hz
800 x 600 @ 114Hz
640x480 @ 130Hz
So unless you are running it at 800x600 you won't be able to get higher than 90Hz. I am known for being able to spot the slightest flicker in a monitor and am more than happy with 75Hz.
If you want a refund then you will have to go to Simply since it is them you have the contract with.