If I don't want to use Great Lakes or Nelnet is it possible to make a payment with another loan servicer?
Yes you can. You can also get a 0.25% interest rate deduction when you  participate in automatic debit.
Well I am having trouble making my loan payment. What can I do when I am having trouble making my federal student loan payments?
The section Trouble Making Your Federal Student Loan Payments  will provide the information on what to do if you are having trouble making your student loan payments.