HSA - Minimum balance requirement question

My HSA plan required a minimum balance of $1,000 to transfer funds to an investment account.

As of this year, I am no longer enrolled in that insurance plan so I am not contributing to the HSA.

Now, there's a $3 monthly fee if I don't keep $3,000 in the savings account.

My question: What can I do with the remaining money in the savings account?

Am I still supposed to be keeping a $1,000 minimum? Can I transfer it to the HSA investment account since I'm no longer contributing to the savings account? Do I start using the funds for medical expenses instead of getting a $3 fee until the account hits $0?

I called customer service, but they didn't have a good understanding of what I was asking due to the language barrier.