There is perhaps no thornier issue in consumer banking than overdraft protection.

Banks see it as a valuable service, which lets customers keep using their debit cards for purchases and ATM withdrawals in exchange for a reasonable fee.

For consumer advocates, the idea of charging a customer who has run out of money is like kicking someone when they are down. The average overdraft fee is $33.38 per transaction, according to 2017 Bankrate checking account survey.

Ultimately, it's the customer's decision to choose overdraft protection. In 2010, policymakers forced banks to make it an opt-in service.

Should you opt in to overdraft protection?

Ultimately, opting in has two major benefits. It protects those who worry about finding themselves in the embarrassing situation of having their card declined. And it provides a temporary, if expensive, float between paychecks. People often turn to it to pay bills for essentials or emergencies.

That's a problem, according to Pew Charitable Trusts. Regulators intended overdraft protection for occasional shortcomings.

"Overdrafters have a different perspective: A third of them see it as a way to borrow money when they are short on cash," Pew wrote in the study.

Also, it is important to remember that overdraft protection covers debit card transactions and ATM withdrawals, not checks or other automatic debits from your account.

Although you have to opt in for the service, some people don't always remember doing so.

The Pew study found that nearly three in four people who overdraft do not understand that they have the right to have transactions declined without a fee if their account does not have sufficient funds to cover a debit.

The problem is that fees can add up quickly if you didn't realize you are overdrawn on your account. Imagine getting hit with a fee for every swipe — a $4 latte in the morning just became a nearly $40 latte. Your $10 lunch is now nearly $45, and so on. Costs can balloon quickly.

Some banks and credit unions have restructured their programs to be more consumer friendly and avoid this pile-on situation.

For instance, Wells Fargo announced in November that it would no longer charge an overdraft fee on transactions of $5 or less that overdraw an account. Other institutions have a daily limit on how much it will charge you for overdrafts.

Call your bank and figure out if you are opted in and ask them to explain its policy.

If you are looking for a less expensive way to ensure that you won't be turned down for a purchase or face hefty nonsufficient funds, many banks and credit unions allow you to link your checking account to a credit card, savings account or line of credit.

Also, digital tools make keeping tabs on your checking account easier than ever. You can check it regularly, but you can also set up text or e-mail alerts that tell you when your account drops a certain level. Many banks offer multiple alerts.

For instance, you can set one up for when your account drops to less than $75 and another for $25.

Be sure to have one set with a good cushion given settlement times on transactions.

Robert Barba writes for Bankrate.com.