You need to do a device WIPE on the 9300, and then create a different BB ID for that device:
KB05099 Steps to take before selling or after buying a previously owned BlackBerry smartphone
KB26694 How to change the BlackBerry ID on a BlackBerry PlayBook tablet or BlackBerry smartphone
Then the 9300 will have a completely separate account of its own for all things.
Occam's Razor nearly always applies when troubleshooting technology issues!
New to the Community? Click here and also here for helpful guidance. Also please click here for additional helpful information to guide you as you proceed. I always recommend that you treat your BlackBerry like any other computing device, including using a regular backup schedule...click here for an article with instructions. If anyone has been helpful to you, please show your appreciation by clicking the button. Need a reference to BB10 OS/SR versions? Click here. Need a specific BB10 AutoLoader? Send me a private message.