Make this simple.
1. As you chose to use an agent rather than dealing directly with OS, contact Expedia and note that as your flight was cancelled by OS, you elect a refund. Nothing more. Do not cite rules and do not tell Expedia what you do not want. All of that is confusing and not necessary.
2. Wait 7 days.
3. On the 8th day, file a chargeback dispute with your credit card issuer (bank). Provide copies of your e-ticket receipt, the notice of cancellation, your request for a refund, any denial of the refund or a note that you have not heard back. Nothing more.
Keep it simple, in writing, and complete. The easier you make this, the more likely this is to happen and to happen quickly.