no service most days

I have been with Virgin Mobile for almost 6 years! And lately I have very bad or no service at all. I phoned Virgin Mobile and was instructed to chose Cell C as service operator but more than 50% of the time the service is unavailable, and then I am unavailable and cannot get hold of anyone or they of me....this has been very frustrating and sometimes dangerous when I am on the road or on holiday and my phone does not work. I need to get better service or I am leaving Virgin Mobile...dont know if they are busy closing down....but the closest Virgin shop is 300km from where I live and obviously I cannot phone the call centre when my phone does not work!!!