Need help in jailbreak again iphone 6+ ios 9.3,3

Hi
I have Iphone 6+ ios 9.3.3 (it cames origanly with this version), was jailbreaked by pp25 pangu english without computer.
I have read that it can't be jailbreak again in that way... Is it true?
Is it posible by any tool with computer?
There is any chance to upgrade/downgrade to any iOS version and jailbreak it ?
Thanks to any helper...