PlayStation Account Recovery – Cannot Change Old Phone Number

I am writing regarding an issue with my PS4 Slim account related to phone number verification. My partner in America originally set up this account using his US phone number. I no longer have any contact with him, so I cannot receive the verification codes that are now required to access or change the phone number on the account. I am currently located in Australia and would like to change the phone number on the account to my own Australian number. However, every attempt to update the phone number still requires a verification code to be sent to the American number that is no longer accessible to me, so I am effectively locked out of managing this security setting. I first encountered this problem one day ago and have tried to contact PlayStation/Sony customer support, but I have not been able to reach them due to their working hours and the fact they are closed on weekends. I request that my account be verified through an alternative method and that the old American phone number be removed and replaced with my current phone number in Australia, so that I can regain full and secure access to my account.