Is there any way to cancel it if I have cosigned on a loan?

No, you cant. Lenders won't let you cancel it. This is why you should always think 100 times before cosigning on a loan. If the primary borrower fails to repay the loan, then the lender will catch your collar. You're stuck dude. Sorry!!! Can't help you.

some loans have T&C that is a program that enable a cosigner to remove his/her name from a loan, after a certain time. It can be after a 2-year period.
You can also convince the primary borrower to refinance the loan and this time, don't cosign it. :-)

Depends on the loan term and condition. technically, the cosigner can't withdraw his/her name in the middle of the loan life. Because the lender needs a safeguard from where they can get back their money. What happened? Why are you thinking like that? For whom you have cosigned the loan?

One good way to do it is, if you have good relation with the borrower, ask him/her to refinance the loan, without your name this time.