But the first thing they'd do even if you didn't jailbreak would be to restore your device and pull a backup from iCloud. If you want to keep your jailbreak, then they can't help you, because who knows if the latest version of iOS included a patch for your problem, a tweak you installed borked the phone, or if Apple borked it?

And as far as I’ve seen when it comes to jailbreaks, anything but the most obviously mechanical problem is caused by the jailbreak.