Account Hacked - Primiray Console option "Hijacked"

On December 23rd, I was playing and a message saying I was disconnected cause I logged on another console appeared.

I immediatly freaked out and contacted @askplaystation Twitter support, explained what happened and they assured me it was not a hacking problem, it was a local account problem and that I needed to delete my account and recreate it again on my console. Nevertheless, I reset my password to a very strong one.

Thought out the following days, I kept having the same problem, same error message.

Since that day, my kids couldn't play the games I purchased on my account. I thought it was related to my PSN Plus having expected around the same date.

Today I called PSN phone support and they gave me the terrible news: someone hacked on my account, and configured another PS4 console as their primary one!!!!

Therefore, I can't upgrade my own console back to my primary console!!!

I contacted phone support, and they said I had to fill a online form in PlayStation.com, asking for a reset of the consoles as primary. Problem is the form asks for the PS4 Serial!! I don't have the serial of the console that the hacker is using!!!!

How can I fix that?

I ask Twitter support but they are not answering!!

HELP PLEASE, folks!!!