When you sign a finance agreement of any sort, you are signing a legally binding contract to pay the finance company an amount each month for a certain number of months. If you want or need to get out of that commitment, you are breaking a legally binding contract and there are consequences.
Usually, the finance company will agree to let you out of your contract if you pay a penalty fee. Depending on the type of finance, that fee may be quite small or quite large. Different finance products work in different ways, and there are significant differences if you want to cancel your contract early.
On a purchase product (like a Personal Contract Purchase or Hire Purchase) or a personal loan, if you want to cancel the agreement then you'll have to settle the outstanding balance. If you have borrowed the money over four years but want to cancel the agreement after three, you will basically have a years’ worth of payments that need to be paid off.
The good news is your settlement figure will be reduced somewhat because you will save money on interest.