They can put notices in the papers about changes in the interest rate and it is your responsibility to pay for the loan at that rate. However, they cannot register a default and they should not add any penalties until after they have written to you about the changes and requested that the monthly payments are changed. If you have not changed the monthly payments, then it is possible that the term of the loan will increase beyond 84 months. In my opinion, it would be unreasonable if you are being asked to settle a large deficiency in a short time and you should consider asking that the term is increased instead but you should avoid taking out a new loan to settle things if possible.