Is it safe to jailbreak my iPhone 4s?

I have an iPhone 4s with sprint and I was wondering if it is safe to jailbreak it because a few months ago I jailbroke it with green posion and it worked for about 2 days then it woulnt let make call or send text or download apps from installous. Sprint and apple couldn't figure out what was wrong or how to fix it (i deleted cydia) so they just gave me a new Phone. After that my dad said if I jailbreak it again I'm not getting a new one, so I want to know when is it a good time to jailbreak it with guarantees of it not doing what it did to my last iPhone and what program should I use next time?

Use redsnow next time.