When the phone rings and the caller threatens to shut off your electric, natural gas or water service in just a few minutes because of an unpaid bill, you pay attention. That’s why telephone fraudsters impersonate utility employees — they can rush you into taking action before you have a chance to think about it.

“From what we hear, the pitch is pretty scary and very high pressure to pay immediately — by wire transfer, debit card, even gift cards — or they’re going to turn off service within the hour,” said Katherine Hutt, director of communications with the Council of Better Business Bureaus (BBB).

How scammers make big bucks off unsuspecting victims

The crooks are targeting both businesses and homeowners, and unfortunately, meeting with great success. While the median monetary loss for all scam victims is $274, the median loss for a utility scam victim is $500, according to the BBB’s 2017 Scam Tracker report.

Fraud.org, the website run by the National Consumers League (NCL), reports a “significant spike” in complaints about utility imposter scams in recent months.

“The pitch can be very convincing,” said NCL Vice President John Breyault. “When even savvy business people can be tricked, it shows that no one is safe.”

Scammers fooled Art Allen, who owns a Toyota dealership in Bastrop, La. Earlier this year, the crooks called and said his electric bill was past due. His electric service would be turned off, they claimed, unless he paid $2,000 immediately via Green Dot MoneyPak cards.

Allen was suspicious, but his office manager wasn’t around and the caller, who had all of his account information, was insistent.

Get the better newsletter. This site is protected by recaptcha

“It’s almost as if they had a copy of my bill in front of them,” Allen told NBC News BETTER. “I thought something was off, but I just couldn’t risk having the power turned off on a Saturday, our busiest day.”

With millions of dollars being lost, more than 100 utilities across North America have joined together in a consortium, Utilities United Against Scams (UUAS), to warn customers. So far this year, UUAS has received reports from more than 15,000 people who’ve lost money to the imposters. A few large companies have been taken for as much as $15,000. UUAS Executive Director Sheri Givens says the scammers are successful because they’re “aggressive and cunning” and often do social profiling to know a lot about the businesses they contact — whether it’s a restaurant or a doctor’s office.

“The say they’re going to roll a truck in the next 30 to 45 minutes and cut off service unless you pay right away,” Givens explained. “These businesses can't afford the financial loss they’d incur if their entire restaurant or business was shut down with all those customers or patients there at that time.”

Instructions to pay by prepaid debit or wire transfer is a red flag.

How to Spot the Scam and Protect Yourself

The scammers work year-round, but the BBB says they’re most active in the winter and summer months, when people can’t go without heat or air conditioning. Here’s how to spot the imposters:

Never pay over the phone in response to a call, especially when you’re threatened with a service disconnection if you don’t pay immediately. A utility will never do that. If you’re getting pressured, hang up and call the customer service number on your utility bill — this will ensure you’re speaking to a real utility employee.

Before shutting off your electricity, natural gas or water, the utility will send you one or more disconnection notices in the mail, and give you several bill payment options, typically online, by phone, automatic bank draft, mail or in person.

Utilities don’t accept gift cards and they never require customers to buy prepaid debit cards, like Green Dot and MoneyPak, to pay their bill. Instructions to pay by prepaid debit or wire transfer is a red flag.

Don’t trust caller ID, even if it shows the name of your utility company. Crooks know how to “spoof” caller ID to make it read whatever they want. It’s another sneaky part of the scam that fools a lot of people.

If you’ve been burned by a utility scammer, file a complaint with the Federal Trade Commission and the BBB Scam Tracker.

Want more tips like these? NBC News BETTER is obsessed with finding easier, healthier and smarter ways to live. Sign up for our newsletter and follow us on Facebook, Twitter and Instagram.