How do I turn off the autopay for my dept/student loans from my returns?

When you go through the File tab you can pick how to get the refund, either by check or Direct Deposit.  I guess you must have put in the loan bank info in there.  Go though and enter your own bank account and routing number.  

If you have not filed yet or your efile rejects, you can change your refund method and bank info by going through the File tab again.  If your return was Accepted then it's too late to change it.  If your bank rejects the deposit the IRS will mail a check to the address on your return.

See if this helps

https://ttlc.intuit.com/community/accessing/help/how-do-i-change-my-transferred-direct-deposit-information/00/27040

Unless you are in default and the IRS is automatically keeping your refunds to pay the loans.  Then there is nothing you can do except catch up and pay on the loan.