It only takes a little bit of crud to ruin your headphone jack. Also, it can only withstand so many insertions and removals before the contacts will wear out. The manufacturers love it when consumers assume that means the phone is used up.
It can be fixed.
It is tiny, and the repair calls for the right tools and a steady hand. Exactly what you'll find a PhoneFreaks. A PhoneFreaks technician will disassemble the phone and perform the replacement right in front of you.
The repair usually takes about half an hour. The replacement is fully tested for clarify and quality. That's Rock and Roll.