Can Sally Mae let me pay off my student loan in less time?

I have 3 loans consolidated with Sally Mae. The original amount I had in loans was $12,400 but when you had interest it goes up to $40,000. That is if I pay the amount they are telling me to pay, which extends to the year 2022. I would like to pay it in 6 years, because the interest is a little over 6% which os not that bad. I've been paying for two years now and it all has gone to interests. Since Sally Mae's service hours are only from monday to friday I wanted to ask if there is anyone outthere who has done this. I appreciate all your help. :-)