My site is hacked again

Hello, my site has been hacked again.
This is the third time that I have communicated about this and I ask for your help since at no time am I notified that the site has had any security or similar violation.
I ask you for confirmation regarding what you suppose is the point of origin of these attacks and how to solve it since this site is on your hosting, it has the security plugin active, the updates and practically everything they recommend, even so it has been hacked for the third time.
I have my suspicions regarding the contact form as I have been sent multiple strange emails in the past.