request to speak to a manager

after speaking to 3 customer service representatives, none of whom could help with a bill that is over charged, I requested to speak to a manager . The customer service rep just puts me on hold indefinitely. after 15 minutes per my cell phone log, they just never come back. I need to speak to a manager about an erroneous bill and cancel my service. The customer service rep said I cant cancel my service!!!!! Luckily your phones are all recorded and you have proof that I requested my service to be turned off and the customer service rep said no!!!!! The person who never came back on the line was ASANELE.