MOR does not let to delete users who made at least 1 call in the past.

WHY?!?!?

The answer is simple - because deleting user with calls will ruin the billing.

Simple example

Let's say we have 2 (TWO) users U1 and U2 and 1 (ONE) provider P1.

During the month one user U1 dialed 20000 calls and another user U2 dialed 10000.

For the sake of simplicity 1 call = 1 EUR worth.

So user U1 should pay you 20000 EUR and user U2 should pay you 10000 EUR. Total 30000 EUR.

You sell with 100% margin, so that way you have to pay 15000 EUR to your provider P1 for the calls.

And 15000 EUR is your profit.

Imagine now what happens when you delete user U1 from the system with all his calls.

We have such situation:

During the month user U2 made calls worth of 10000 EUR and you see that you should pay provider 50% of that - 5000 EUR.

BUT!!!! Provider sees that he sent 30000 calls and not 10000 as you say. And these calls worth 15000 EUR.

So you will be in -10000 EUR after 1 month!