Those companies outsource the actual handling of loans to these 9 third-party servicers, who then take over all sorts of functions, such as sending bills and accepting payments.

They're also supposed to help borrowers with problems about their loans, and borrowers go to them to change payment plans, enter deferment or forbearance, apply for forgiveness and take care of other matters.

But that doesn't mean that things go smoothly for borrowers with their loans, even if they have asked servicers for help.

Related: The people there to help with student loans are less than helpful

With plenty of stories about instances of dishonesty, or "about a servicer unfairly optimizing for profit, harassing borrowers, or violating some other regulation," the Student Loan Report went to the Consumer Financial Protection Bureau's complaint database and analyzed what it found—a total of 5,344 complaints against student loan servicers so far in 2016.

Then SLR divided the number of complaints by the number of borrowers managed by each servicer, and also reported the total number of complaints made against each servicer for federal student loans, private student loans, and both combined.

Data were not available on the number of borrowers for each of the five not-for-profit servicers, so there is no average number of federal loan complaints per 100,000 borrowers.

If you want to see how your servicer stacks up, take a look below, from worst to best.

9. Navient

Navient came out the worst, with 1,317 complaints made about federal student loans, which breaks down to 19.54 complaints per 100,000 borrowers. When you add in private student loans, Navient had an additional 1,596 complaints against it, for a total of 2,913.

The Student Loan Report wrote that Navient has "had numerous violations and lawsuits over the past few years. In 2015, the company had to pay $97 million to the Department of Education, Department of Justice, and the Federal Deposit Insurance Corporation for charging extra fees to military members. To make matters worse, in August of 2015, the CFPB alerted Navient that they were considering pursuing legal action for misleading servicing practices. Aside from those two cases, the company has faced a number or smaller lawsuits and allegations that have done little to improve its reputation."

8. PHEAA (FedLoan & AES)

With 907 complaints against it so far this year just for federal loans, PHEAA had 10.86 complaints per 100,000 borrowers—better than Navient, certainly, but then it had 8,350,000 borrowers compared with Navient's 6,740,000 borrowers.

Overall PHEAA had 1,385 complaints—it logged another 478 complaints about private loans.

7. Nelnet

Although the five not-for-profit servicers collectively actually finished third from the bottom, with a surprisingly large number of complaints in aggregate, when all servicers were considered individually Nelnet claimed that spot with 406 federal loan complaints (an average of 6.51 complaints per 100,000 borrowers) and 87 private loan complaints.

The Student Loan Report pointed out that, "despite private student loans making up only around 10 percent of the total student loan market, 42 percent of all complaints against servicers were made regarding private student loans."

6. Great Lakes

Great Lakes had an average of 3.09 complaints per 100,000 borrowers on federal loans, with 255 complaints from a total of 8,260,000 borrowers.

When you add in the 46 complaints it received about its handling of private student loans, that gave it its sixth-place finish.

5. MOHELA

MOHELA is one of the not-for-profit servicers, but you'd never know it by its complaint record—the report said that, "out of the five not-for-profit servicers, nearly half of the federal complaints were made against MOHELA."

MOHELA racked up 95 federal loan complaints and 26 private loan complaints so far this year.

4. EdFinancial/HESC

Another not-for-profit servicer, EdFinancial/HESC had 49 complaints about federal loans and 11 about private loans.

The report pointed out that "on average, only 1 out of every 10,585 borrowers made a complaint to the CFPB about his or her servicer (assuming there were not multiple complaints made by one person). Though this may seem pretty low, it only includes complaints made to the CFPB. Many borrowers may have filed a complaint somewhere else, or not at all, when they ran into trouble."

3. CornerStone

Not-for-profit CornerStone had 49 complaints about federal student loans and just 4 about private student loans.

2. Granite State

Second place was captured by Granite State, which managed to have just 16 complaints about federal student loans and 2 about private loans.

1. OSLA Servicing

If you're looking for a servicer, you probably want to stop here. OSLA had zero—that's right, zero—complaints, emerging unscathed in both federal and private student loan categories.

Said the report, "Though this may be because the company has exceptional customer service and gives its best effort to help borrowers, it is unusual to see a student loan company receive no complaints at all due to the nature of the business. We are eager to see how OSLA fares in 2017."