Overpaid into two ISAs

I've accidentally overpaid into two ISAs with different banks. I've read that I should contact my bank to sort it out, but I am not sure if having two banks is an issue. I've been unable to speak with an agent on the helpline, what should I do? Thanks.

Hi,
The 20k limit applies each tax year irrespective of how many accounts so you will still need to contact one of your providers to advise them of your error.
Thank you.