RAIN sim swap confusion

Last year November I lost my sim card so naturally I requested a sim swap. this is were it's gets really strange. I was never told that I should wait 24hrs for the sim swap to take effect, so I proceeded to activate the sim through the rain online activation and I ended up with two sim that reflect on my account.

I was told to cancel the old sim but I refused to my detriment and argued that this should have happened automatically as this was a sim swap.

I understand I made a mistake by activating the sim but to my defense, that information was to given to me.

so now I'm being billed for the new sim which I'm currently using and the old sim that I lost and has no history of usage since the day I lost it.

I find this not being fair at all and rain customer support not being helpful at all in correcting my situation.