Excessive billing and no assistance

I have had a contract for the past 5 years and as of of July this year the account has more than doubled. <br> Called the call centre three times, sent e-mails, raised query on their facebook page - twice, the assistant at one of their outlets tried to help me by sending e-mail requests, called the billing department, held on for 15 minutes - no answer.<br> I offered to call someone that could assist, all they need to do is supply contact name, number and details and a convenient time, was told to call the call centre - BUT THEY CANNOT HELP ME!<br> <br> this has been going on for two months. the worst service possible.