Blocked Line

My line keeps getting blocked. I have no lock or limit on my line, but today, i have had to call twice to get them to remove a block. now for a third time my line is blocked. I am unable to call or use my phone at all due to a glitch on their side. It is incomprehensible that this constantly happens, without any proper explanation. My job requires that i am always contactable and always able to use my phone, not being able to use my phone, is not jsut an inconvenience, it prevents me from being able to work!