Billed for SMSes I did not send

Telkom Mobile billed me for SMSes to the UK. I do not have this number on my phone. I asked them to provide details such as the contents of the SMSes and the places I sent them from. Telkom's response is that I should institute investigation myself. The call centre agent would not even transfer me to the manager as she believed I would get the same response.<br> <br> This is the second time this has happened. They close the previous investigation without giving feedback. I am not prepared to pay for that part of those SMSes. I have requested them investigate but they insist I should be the one to investigate (Case ***0).