Step 1.  Call the number on the bill for the billing department.  When you reach a billing rep, get the name of the person with whom you are speaking and let them know that you are disputing various charges on your bill.   If the employee refuses to give his/her name, ask for the employee number.

Step 2.  Tell them to enter the details of the conversation into their "notes".  Every customer has an account which has a section for notations.

Step 3.  Fax a letter to this person.  This is by far the most important step.  You must draft a letter that illustrates the circumstances surrounding the charges and the exact amount that you are disputing (as a precaution, confirm receipt of the fax by following up with a phone call within the next 48 hours).  

Step 4. DO NOT refuse to pay the entire bill unless it is the entire amount that you are questioning.  Pay the charges which are accurate and withhold the amount you are challenging.

Step 5.  Contact the state regulating agency and send/fax a copy of your letter to them.  Every state is different and Verizon will inform you of who to contact.

Know that at this point it is ILLEGAL for the phone company to take any action until against you including discontinuing your service or blemishing your credit until the matter is resolved

From here it will depend on your state.  In all cases, they must give you the name and address of the appropriate regulatory agency to send your appeal to.  In some states, the carrier is required to inform you in writing of your right to appeal.  Regardless, Verizon or any other phone company will not be able to do anything until a decision is rendered by the agency.

You may have to send in the disputed charges to the state regulator pending resolution of the complaint.