COLUMBIA, Mo. -

Millions of consumers look to upgrade their cell phone each year, but what do you do with you old phone?

Many let it collect dust in a drawer, but others look to make some money by reselling it online.

Jumping on Craigslist in an ABC 17 News Special Report, we found dozens of cell phones for sale online in Mid-Missouri.

Purchasing four cell phones, two smartphones, and two older style cell phones, ABC 17's Kristie Reeter was looking for data that may be left behind.

In the two smartphones not much was left behind. In one there was a number left in the call history, and in the other there was an SD card still inside.

SD cards store pictures, videos, and music. Tech experts recommend removing SD and SIM cards from phones before selling them.

Hooking the SD card up through a computer, we couldn't find anything left behind.

In the two older style phones there was a lot of information.

In one Pantech model the seller deleted her contacts but left behind pictures and text messages. Reaching back out to the seller, she said she did a factory reset, but noticed right before selling the phone that the contacts were still there. She deleted them, but those pictures and text conversations remained.

In the other phone, a Motorola flip phone, there were contacts and text messages. The seller said he had gotten it from a friend and never used it before upgrading to a new one. 

While leaving behind contacts, texts, and pictures can be damaging, nowadays many people store passwords on their phones to social accounts, email, even bank accounts.

Ryan Wilkey with Midwest Recycling Center (MRC) says, "Identity theft is one of the fastest growing crimes right now because of people's ignorance to the subject."

MRC is certified to recycle everything from electronics to appliances. While MRC has procedures put in place to either shred cell phones or wipe them clean before they are resold, Wilkey says there are steps people can take to make sure their cell phone is wiped clean.

For those with iPhones you will go into "settings", "general settings", scroll to the bottom and hit the reset bar. There will be several options, but the best is going to be "erase all content and settings." After it powers back on make sure personal information has still been left behind.

When it comes to androids it's a similar process, but each phone is different, so check the owner's manual. Most times it's under "settings", "privacy", "factory data reset", and then reset phone.

Experts say these simple steps could prevent you from being the victim of identity theft.