Here is my suggestion. First, continue to press your TA. If your TA wants your return business, and they usually do, they will get back to you quickly and get this resolved. If your TA does not do this, I suggest you contact the TA's manager and speak with them.
If this doesn't work, and the TA won't work with you to resolve the situation, then you should go through the Customer Service Department at RCI. Do not write the chairman or President of the company. I know we would all like to think that if we write to the "top" guy, they will read our letter, become enraged at the injustice and run downstairs and personally fix the problem. Well, that really doesn't happen in a huge company like RCI. Their letters are screened and complaint letters are sent to the Customer Service Dept. where they belong.
Write your letter to the Customer Service Dept., be polite and do not rant or rave. If you do write a mean spirited letter, they will believe they cannot retain you as a customer and will be less inclined to solve your problem. Explain your situation and that your TA has not provided you with satisfaction on your complaint. Provide copies of all your supporting documents, including proof that you paid the fuel surcharges and didn't receive a refund.
Having dealt with the RCI Customer Service Department at RCI, this is not a quick process. It will take a few weeks for them to get back to you. If you haven't heard from them in a month, I suggest you call the Customer Service line and inquire. Be advised that the people that answer the phone at RCI Customer Service are not the actual reps that work on your problem, the actual reps do not give out their phone numbers. This keeps them insulated from customers constantly calling them. The front people take your phone number, message, and all your information, and pass this along to the rep, who will contact you.
Good luck and I hope you get this resolved.