Can a company refuse to letan employeecancel their health insurance when the cost is deducted from thetheir paycheck?

1) Generally, once someone is in a health plan, their enrollment may only be  changed either (a) during the open enrollment period annually (at which point the employee could drop the plan) or (b) when there is a life status change, such as marriage, divorce, birth of a child, etc.

2) Many employee health insurance plans will only cover employees who work over a certain number of hours per week--typically 25. This is not to say that your company's plan couldn't cover part-time employees, but there's a reasonable chance that you can't be covered working only 8 hours, and this is something to check with your HR dept and/or directly with the insurer.

3) While you're not working for free--getting health care is itself valuable compensation--clearly you're not being paid enough to live on. As a practical matter, if you're only working 8 hours per week, you could take another full time or 2 - 3 part time jobs and/or work freelance. You might want to consider taking additional employmenet without regard for whether it has health insurance--i.e. look for the highest rate or salary you can get--while working that current job just to maintain health coverage. I actually do something similar: I have a part time job that provides me little more than health coverage, but that way, I don't have to worry about buying it myself  as a sole practioner attorney.