To put a Wasion in postpaid mode, you'll need the 20 digit token from the vendor you bought the meter from
and an optical probe
Download the Wasion software here
Then setup under the communications tab which COM port to use
Then:
1) under the STS tab
2) set Vendor to Manual
3) enter your Token
4) Click Vend
you should see the text POSt-PAy written on the LCD screen of the meter