Cancel an Insurance Policy With Geico

I pay my GEICO auto insurance every six months, save some money because instead of paying monthly. Here is one thing I’m going off to U.S. for 3 months and I need not assure my car but I have already paid for 6 months. Can I cancel my car insurance and get the rest of money? Do you have a method for freezing these situations? If I cancel my car insurance, I will collect some money? How do I calculate this? Need to be answered, Thank you.