Sounds like a fatsia. Picture?

I'm thinking Ficus elastica, or rubber plant. If it is that, you can cut it back to wherever you like, but be aware it will drip lots of sap for some time, so you may want to surround it with newspaper or something until it stops bleeding. It will most likely produce lots of new shoots in the part of the trunk where you've cut it, so think about what shape that might make and cut it back to where it will look okay with a cluster of bushy new growth in a year.

Possibly also a Fiddle-Leaf Fig (Ficus lyrata), which can be treated the same as the Rubber Tree.