Hi bethdosser ans welcome to the forum:
I have more questions than answers to your problem, so maybe you could answer these to help clarify the problem.
1) Is Benji actually jumping over the fence, or is he climbing up onto something and then over?
2) Is the fence a chain link or wooden fence and how high is it?
3) Does Benji come back on is own, or do you have to go out and bring him back reluctantly?
4) What other form of physical activity does he get daily and for how long?
5) Most importantly, is he being aggressive to anyone or anything while he is out?
I'm not a big fan of the shock collar, as the name states, it sends a shock of electricity throughout the body, to which I feel will have effect on the heart over time.
My first dog was a BorderCollie/Shepherd, and if it wasn't for the 5 foot wooden fence around our backyard, she would have been gone as well.
Heaven forbid you were to open the front door and something/anything catch her eye because she'd be gone.
I really hope this problem will get fixed

All the best.