No feedback from company

I received 4 months high bills from Vodacom. I phoned them regarding this and they asked me to send a mail and attach certain documents. After the initial mail I send them another 2 and a fax and still no response! I only want a detailed invoice and them to investigate my query! I can't believe that a known and respected company has such poor customer service!!! <br> <br> Regards<br> Dewald du Toit