I have to press *73 to get the line back

[jalalfares]

Hello
A month ago started to have a weird problem with my line. People can't reach me so I open the phone to see if the line is working (dial tone) and I hear no continuous tone but rather beeps similar to VM beeps or busy beeps. So what I found would solve this is if I press *73 and then the tone comes back normal and I am able to receive calls normally.
But in a few hours and randomly this happens again all alone.
I know *73 is to deactivate call forward but I didn't activate call forward, it's like it's being activated automatically.
Can you please tell what is happening, I need the line receiving all the time for my work. Thanks a lot
I am trying disabling the provisioning and debugging on my ATA to see.