Manual refill does not allow negative numbers

As admin, sometimes I need to reduce the prepaid balance manually but astpp does not allow negative refills (topups). What’s the reason? The admin should be able to add, substract and zero the prepaid balance without any restrictions.

I asked about something similar about giving a client a “credit” on their account.

https://forum.astppbilling.org/t/adding-credit-to-an-account/