Outage is a constant problem, how to get out of contract?

We are a small animal hospital and for a month we have diwsconnected phone  and internet service. It a constant problem. Tech came here to fix the problem.  When they come every thing worksm however we have service interuption for few minute and then  become normal. Comcast blames that we have problem with our line. We were with AT&T and never a problem .

How to get out of service contract with comcast?