You can sue anyone who has legally wronged you. If you did sue them, you would have to argue that because of the constant interruption in service, they owe you the money you have already paid for that service. Since this is not what you are looking for, it would not be advisable to sue. In addition, your current problem would not be solved. Your best bet is to call them again and speak with a manager. Tell him/her that if your problem is not fixed within a reasonable amount of time, you would have no other choice than to cancel your subscription.