If you've enabled the Walmart Fast Tag, then you must set your standard processing schedule to Eastern Standard Time. If this is not done, then Deliverr will auto-upgrade orders received, which you will be charged for.
To correctly set your standard processing schedule, please follow the below four steps in Walmart Seller Central.
Step 1: Log into Walmart.com seller central, and click 'Settings', 'Shipping Info'
Step 2: Under "What timezone do you primarily ship from?" select 'Eastern Standard Time'
Step 3: Scroll to the the bottom of the page and click 'Save'