Do I Have To Pay Them Back For Insurance?

I worked for a company for 5 years. In April, two days after hitting 5 years with them, my dad got sick and went into the hospital and then I got sick and had to go on disability. My former employer gave me all the state of California paperwork and told me they would be collecting my insurance premiums every pay period and required me to fill out a credit card authorization form for them to charge. I provided them with the credit card authorization form and then pay roll came and went but nothing was deducted. I reached out to hr and they said they’d be pulling it the next cycle. Two more weeks of me being on disability come and go and there is still not withdraw for the premiums. I reached back out to hr and they said they’d reach out to billing. I said okay and a couple more weeks went by and nothing was pulled. I reached out again and hr said billing would let me know when they were ready to withdraw the premiums. This was 6-8 weeks into my disability so I just said alright they will reach out I guess. Fast forward 6 months and my health made it so I could not go back to that type of work and had to seek alternative employment. I put in a resignation letter stating I would not be returning from my leave. They sent me an exit interview and some half ass document stating I never had to work off the clock they wanted me to sign (I did have to work off the clock, they’re in a current lawsuit for this) and I signed neither. Fast forward a week and they called me and said I owed them for 6 months of insurance premiums. They left a voicemail and sent an email stating what they want me to pay and offered to take payments.

Do I actually have to pay them back or is this something they should be writing off as it was literally their own clerical error? I tried multiple times to pay it and they didn’t want it. Now I don’t have it and I’m just curious what my legal rights are before discussing with them.