Bernzomatic propane tanks can be refilled.
To refill Bernzomatic propane tanks you can buy a propane cylinder refill adapter that you screw onto the small propane tank and then attach it to the bigger propane tank.
Then you turn the valve on the big propane tank on and allow it to refill the small Bernzomatic propane tank and then turn the valve back off when it's refilled.
Just be careful to not overfill it and it will be okay.
I've refilled some Bernzomatic propane tanks this way and it's not any less safe to have a refilled tank than it would be for it to be filled by the company.
You just have to be careful and know how to refill the propane tank safely and it will not be a problem.
Just make sure the valve is working properly in the small propane tank and make sure the small propane tank is in good condition and not rusted out.