NEDBANK ACCOUNT BLOCKED

my son is working on the yachts in Asia and his bank account has been blocked. They said he must submit a W-8BEN form, which he did a few times. He is currently not being able to access his bank account for almost 2 - 3 months. I phoned on behalf of them because he only has a whatsapp number. I asked them if they can please phone him on his whatsapp number but they said they cannot. He even emailed them but to no avail. He tried to phone them from someone elses number as he only has Whatsapp number but all the numbers they gave me does not work from there. He is always out at sea so it is difficult for him to phone. But surely they have his email address and can contact him via email if there is anything they need from them.