The hub motors' top speed is usually governed in the display itself. Everything you can do is done in the display settings. the programming cable thing is for mid drives and thats a different kettle of fish. So, you need to be able to get into your display's settings, which usually involves some kind of multiple-keypress-and-hold kind of thing to let it show its setup screen. What is your display? A picture might be enough to tell us what we need to know.
Unfortunately, additional speed is not going to do much other than to help get you a running start. You won't actually have any more oomph (torque) to make the motor spin harder. It'll just spin faster so you have a higher start speed at the bottom of that hill you just ran up to.
Also, its hard to say whether or not your bike has any more to give. Lets back up a bit to explain using more commonly understood automotive terms: Think of your battery voltage as horsepower. Think of your controller amperage as torque. Horsepower helps your top speed, but torque helps give you grunt off the line. There is an old saying: Horsepower helps sell cars, torque helps cars win races.
With that out of the way, what is your battery voltage? If it is 36v, you may be close to your peak speed already. Especially if you have smaller, 20" wheels on say a folding bike. A 26" fat bike with a 48v battery and an average weight rider can get up to maybe 23-25 mph. Thats with tall 4.5"+ tires.
To get up a hill though, with a hub motor, without losing that head of steam, you need more torque to keep that motor grunting up the hill. Thats where your real improvement will come going up a hill. Unfortunately upgrading your controller - and probably your battery voltage to get hold of a pack that can handle the bigger amp draw - is probably a little more DIY upgrading than you care to undertake to get a satisfying result.
