deduction after cancellation of med aid

Good afternoon

I have recently cancelled my med aid due to financial problems and last month I requested a cancellation certificate of which I received and handed it to my HR department to confirm cancellation. I was told by gems that no deductions will go through but I was surprised when I received my salary advice that they deducted the money of which is not fair because for this month I'm not covered. I'm also worried about what if the same thing happens again this month. I'm already under huge financial strains and need to settle some accounts. I'd also like to know if theyll refund the money deducted last month since Im not covered

Thank you