Yes you can extend it..but you need valid reason..like you again enroll yourself in new program  in  University..

If your university is willing to help you extend your visa, then they know the procedure. They probably want you to give them a reason for your extension. Are there some courses you still have to pass but have no time to since you need to graduate soon? Is your research not finished yet? If the answer is yes to one of the above questions, your uni should help you extend, but most importantly for them, you have to pay for the next semester's tuition (or for how many semesters you want to extend)  and other expenses as well.