When your fixed-rate home loan comes to the end of its fixed period, you could choose to either re-fix or switch to the prevailing variable rate. You cannot extend the term of your existing fixed rate. Instead, your bank will offer you a revised fixed rate which you can accept or reject.
At the end of your fixed-rate period, it's a good time to take stock of your financial situation before deciding on your next move. A lot has likely changed since you agreed to your original fixed-term rate, including your circumstances, financial goals and what's happening in the global market. These are all important considerations for deciding whether to re-fix or switch to a variable rate for your new loan amount.