You must always have at least one bank account linked to your Currensea card. If you want to unlink your existing account, simply link a new one first and wait for it to become active.
You can add a new linked bank in the "Linked Bank" section of your Currensea app. To get to this section, tap your initials in the top left corner of the app. You can then tap "Get Started" under the "Backup Account" section and follow the instructions to link your bank account.
Once the account is classed as live it can be set as "Active" in your app. Keep in mind that it will take 4-5 working days for the new account you've linked to become live. This is due to the length of time it takes to set up a new Direct Debit Instruction with your bank.
Once your new linked account is classed as "Active" you will be able to unlink the old one. You can do this by tapping the account you want to unlink and following the instructions.
If you already have two linked accounts, you can also unlink one of your accounts here too.