I have been trying to edit/update my credit card on Avis in my profile but it keeps saying " We are unable to process your request at the time". Please return to etc.

I tried editing and also adding a new card and all methods failed.
Is there a trick to do this? I logged out and in and turned off my VPN but to no success.
The reason why I want to change the card on my avis profile is, I recently rented with avis and used ANOTHER CARD to prepay for the rental. After I dropped off the rental and few days later, I am charged for tolls and fuel charges on my AMEX card that is on the file. I easily disputed and got the fuel charged refunded and I am in process of disputing the toll charges by Avis because I have proof of all toll charges charged to MY ILLINOIS TOLL TRANSPONDER. Anyway bakc to my main topic and concern, do I have to call to remove add update the card on file with AVIS?