How does claim reimbursement work (specifically for prescriptions)

I recently had to fill some prescriptions prior to my cobra being processed. It has been processed now retroactive to prior to dates of service.

I submitted online for claim reimbursement and the insurance company processed the prescriptions at full retail price (the price I paid) instead of with the plan discount/price adjustments. They also put it towards my deductible even though my deductible was already met. This isn’t how it’s supposed to work correct?

For example, I paid $100 out of pocket. When I look at this prescription on my pharmacy portal, with insurance, they are only allowed to charge $20. I was under the assumption that when I filed for claim reimbursement it would take the allowable amount into consideration and I would be reimbursed $80. However, it processed to insurance as the $100 I paid out of pocket.

On top of that, the $100 was submitted towards my deductible but I already met my deductible. So my account is reading $3,300 of $3,200 deductible met. So I also thought I’d only be subject to the after deductible price which is 20% coinsurance.

This would have meant that the retail cost was $100, which I paid. My plan would have allowed $20 per their contracted price agreement for this medication, and I would have only been responsible for 20% of that allowable price because I already met my deductible and those are the terms of my plan. I was expecting after filing for claims reimbursement I would have only owed $4 and I would have been reimbursed for the $96.

Am I understanding how claims reimbursement is meant to work or am I wrong?