By now you’ve probably heard about Tech Support Scams, where someone calls you out of the blue and tries to convince you that your computer is infected with a virus, that they have somehow detected it remotely, and that the only way to fix the problem is to hand over money, control of your computer, or both.

It’s one of those scams that can easily be avoided with the question, “Who initiated contact?” If they called you, it’s fraudulent.

But what about when you’re the one initiating contact?

When you need customer service from a large company like Amazon, Facebook or Netflix, it’s important to make sure you’re getting their contact information from a trustworthy source. Internet searches might lead you to a correct number, but the internet is also brimming with hundreds of examples of fraudulent customer service numbers, posted by criminals in hopes that you will call them instead of the legitimate phone number.

What happens if you call a fraudulent number? They may try to get your password information to take over your account and lock you out, they may ask you to reveal credit card or other financial account information, or they may take over your computer (with your help) and install malicious software or commit other crimes.

If you need to contact customer service, make sure you’re getting your information from a reliable source. Don’t trust phone numbers that appear in online forums. If you notice zeros replaced with the letter “O” (1-8OO instead of 1-800, for example), that’s a sure sign of a fraudulent phone number.

With some companies, Facebook being the most prominent example, there simply is no phone number you can call. Any problems have to be resolved using online tools. Every single phone number you see listed on the internet as a Facebook customer service line is false information.

The best way to find customer service contact information is to go directly to the company’s website and look for links like “Help” or “Contact Us.” Sometimes there will be options for help via email or chat and no option for telephone contact, other times the phone number will be front and center. It depends on the company you’re dealing with. In any case, to avoid a massive headache and potential losses to fraud, always make sure you’re getting the number from the official source before you even pick up the phone.