Due date mismatch

In this article:

Our numbers are classified by the FCC as wireline numbers. Due to this classification, porting may take anywhere from 3 to 7 business days (more or less) depending on the provider.

If your new provider tries to port and receives a "due date mismatch" error, ask them to select a date at least 5 business days away from the current date selected. This will guarantee the number port will go through.