NEED ADVICE : At-fault car accident, their insurance wants me to pay $25,000

So I was involved in a car accident August 2025 & it was an extremely dumb mistake on my part. I was on the freeway, I looked at my phone GPS on my lap a couple seconds too long and ended up rear-ending someone's Lexus. I had insurance at the time & so did they. Since I was at fault, my insurance agreed to pay only $5,000 in property damages, which is the maximum amount my policy covers. There were zero ppl injuries, fortunately.

Fast forward a couple months, their insurance company (Mercury, which is NOT the insurance company they had at the time of the accident, AAA) is requesting that I pay the remaining balance of the property damages of around $25,000. They've called me, physically mailed me a letter 3-4 times, and somehow found my email address (which is weird, bc this email is not attached to my car insurance account in any way, so I don't even know how they would have found it).

I have a very part time job and don't even make 5 figures per year, so I really have no way to pay this amount.

• Is there anything I can or should do right now to deal with this situation, when I am not in a financial place to make this payment ?

Some other questions :

1. is it normal for the other driver to go to a different insurance company than what they initially had during the time of the accident ? They initially had AAA, but I was contacted by Mercury instead.
2. Is it abnormal / illegal for them to find & contact me via my email address ? especially since it wasn't attached to my car insurance account in any way.

Any help would be appreciated.