You can change your payment method by logging into your employer account and going to Account Settings/Billing:

Click 'Edit payment details':

Click 'Add payment detail':

You may need to "sign in a guest" to see the direct debit option.

Once you have done that, you will see two payment methods listed on the Billing page. You should delete the one you don't want using the bin icon:

You can also use the star icon to set a default if you would like to retain details of your other account rather than deleting it.