1. Make Sure the Phone Works with Your Service
As a general rule, cell phones will only work with a single carrier. A phone built for Sprint won’t work on AT&T, because their wireless signals are different. There are exceptions, so sometimes it’s best to check. Remove the SIM card from your phone and place it in the one you are considering for purchase. No error messages? Continue to the next step.
2. Check that the Phone is Fully Functional
Before you hand over the cash, turn the phone on. Connect to a local WiFi and browse the web. If your current phone has a data plan, you can try the data connection through the cell towers. However, some wireless carriers will automatically add a data plan ($30 per month) when they detect your SIM card using a smart phone.Next, check the camera. Take a picture and view it. Now test the speakers and headphones by playing an Song or Ringtone. Finally, make a test call to a friend. Using both the earpiece and the speakerphone, listen for the sound quality and ask your friend how you sound, too.
3. Check for Water Damage and Screen Cracks
Carefully inspect the device. Is there corrosion on the connectors? This may indicate exposure to water. Look for hairline fractures in the touch screen. Is there dust or fingerprints behind the glass? This means the screen has been replaced.
4. Check Reported Lost or Stolen Phones
After all this inspection, the biggest concern is that the phone is denied service because it was reported lost or stolen. Call your wireless service provider and confirm the that it has a clean ESN/IMEI/MEID. This number is located on under the battery or can be viewed in the phones settings.
If you are able to make a call using the phone, chances are pretty good the phone is ready for purchase.