1. Back Up Your Data
Before you wipe your cellphone of all your data, make sure you’ve backed it up to your computer hard drive or to the cloud.
2. Terminate Your Cell Service
Contact your service provider about terminating your service or switching it to a new device.
3. Factory Reset Your Phone (iPhone)
Next you’ll want to do a factory reset of your phone. This will wipe your cellphone clean of any personal data and restore it to factory settings.
iPhone users can do a factory reset by going to Settings > General > Reset, and then tapping “Erase All Content and Settings.”
3. Factory Reset Your Phone (Android)
Every Android phone is different, including the menus, but you’ll want to look for menu options that look similar to Apps > Settings > Privacy > Factory data reset.
Another option Android users can take is to “flash” their phone. To do this, you’ll need to get your phone into “Recovery Mode” by pushing the right combination of buttons. You’ll need to look up the combination specific to your manufacturer (or device), but usually it’s the down volume button and the power button. Once your device is in Recovery Mode, navigate to Wipe Data/Factory Reset. This might take several minutes.
4. Remove SIM or SD Card
Remove or delete the data on your SIM or SD card located in your phone (if you have one). A lot of data, including photos, can remain stored on the SIM card even after you’ve done a factory reset. Destroy the SIM card or see if it’s compatible with your new device.
5. Double Check
Go through your phone one final time to make sure that you’ve erased all the data. Be sure to check contacts, photos and your calendar, and clear your browser cache.