Depends if it's pre-pay or post-pay.

[jeff47]

I can get insurance coverage before I send in a check. Which means I've received something of value before paying them money.

If your interpretation of contract law was valid then when employees lost their jobs the company would be on the hook for their part of the insurance for the rest of the year

And the ability to drop people for no longer working at the company is explicitly covered in the contract between the company and the insurer.