Exceeding ISA Allowance

Hello, I have a question regarding exceeding the ISA allowance. I have topped up GBP 20,000 in an ISA provider earlier this month for my stock ISA allowance this year. Yesterday, I tried to top up GBP 5,000 fund as general investment (instead of ISA) in another provider, but the money I transferred to the provider has been automatically allocated to the ISA account I have with this other provider because their system has been designed to do so. I did not intend to add the fund of GBP 5,000 to ISA as I am aware I have already used up my GBP 20,000 allowance for the year. Now the provider explained to me that I have oversubscribed ISA because this GBP 5,000 has been allocated to ISA. Could you please advise what I can do to rectify this? I want to be fully compliant with the ISA policy and believe this oversubscription is resulted from the issue from the provider. Thank you

Hi Dian Lu,
The excess payment will not attract the ISA relief and any interest or gain will be taxable.
HMRC will contact you in due course to advise.
Thank you.