How can I combine two HSA into one? How can I reimburse medical expense incurred after the establishment of first HSA but after second HSA?

My HSA was established in January 2024 and funded since then till end of 2024, It was  managed by Bank of America.  I lost my job in 2025 January and cannot make contribution to it. But the balance in that account is always keep as $1000.

There is a medical expense incurred in March 2025 which is $1500. 

I got a new job in May 2025 and be able to make contribution to a  HSA again. But this account is managed by Fidelity.  Now I have $600 in this Fidelity account.

My question is how can I reimburse that $1500 medical expense by both previous HSA and current HSA account?

Can I combine these two HSA accounts into one? What will be the establish date for this combined account?

Thanks