API - HR_PERSONAL_PAY_METHOD_API.update_personal_pay_method

HI,
I am trying to update external bank accounts for employees to add in BIC and IBAN (segments 6 & 7 of pay_external_accounts)
I have followed the following API:

HR_PERSONAL_PAY_METHOD_API.update_personal_pay_method

but I get an error:

ORA-20001: The primary key specified is invalid

Cause:        The primary key values specified are invalid and do not exist in the schema. 

Action:        Check the primary key values before attempting to carry out the operation again.

Here is my code

DECLARE   
   lp_effective_start_date         DATE;     
   lp_effective_end_date           DATE;      
   lp_comment_id                   NUMBER; 
   lp_external_account_id     NUMBER;