Lack of contact

My account is behind and have been been battling since last week to get through to sumbody that can help me. The telephone number on the invoice does not exist. The emails for the accounts department and collections department come back saying rejected by server. I would like to get hold of somebody. My account has been frozen and I keep receiving SMS to say I need to get hold of them, When you do online chat with them they put you through to the department but the other person just puts the phone down. I have been with this company for over 20 years and have never experienced this before. As this is the main email that I use it means that my clients can't get hold of me. I find this very irritating as I am now loosing clients because I cant get hold of you