I have a few custom attributes to extend the customer with bank account information. The attributes are stored in
mage_eav_attribute table. How can I get them via the SOAP API?
Did you try to specify them?
customer.info looks like to have a third attribute which allows you to pass an array of requested attributes. I have no clue about SOAP, so I might be wrong, but if the attributes are not returned,
\Mage_Customer_Model_Api_Resource::_isAllowedAttribute might filter them.