Lied to by representative

My mobile acct was billed $306 for 2 messages made in Canada.  I called on 8/20 and representative advised it would be waived.  I had to call on 9/8 when the bill processed to get the credit applied.  Called on 9/8 to be told they could not waive the fee.  I would like to get in touch with someone in corporate to file a complaint.  Please help.