I got a used phone, but it has someone else's Episode account already on it.

When receiving a pre-owned mobile device, if the previous owner had previously installed and played Episode, then their account may still be active on the device.

It is recommended when receiving a pre-owned device to factory reset the device to its original settings to safely remove all of the previous owner's data. For information on how to safely factory reset your pre-owned device, please contact your cell phone provider or the manufacturer of your device. 

See also:

How do I restart all of my stories? I would like to reset my progress and create a new account.