Bulgarian gsm operator Mtel is cheating with VAT

Mtel, a Bulgarian gsm operator is cheating clients on subscription plans Relax/Comfort with VAT. I use cheating since this 'error' is something that even a dumb fifth grade of a clever third grade will notice and not do. The rate published on the official page declare a price per minute of 0.32 leva.

However in the invoices Mtel prepare minutes are counted as 0.27 leva without VAT. VAT in Bulgaria is 20%, and clearly 0.27 * 1.2 results in 0.324 leva per minute. This wound not have been a problem for a single minute. However Mtel sums all minutes, counts them as 0,27 and afterwards calculates VAT over the whole. This results in additional 0,01 leva being added for every 2 and a half minutes.

Here is an extract from my last invoice - M-Tel - M-tel busy hours 49:43 13.32 levs; adding a VAT of 20% - 13.32*1.2 = 15.984

If they were correct - 49:43 * 0.32 = 49 minutes * 0.32 + 43 seconds/60 seconds (to convert into minutes) * 0.32 = 15.68 + 0.229 = 15.909 = 15.90; even if we round up, which we should not do this is 15.91 or about 0,08 leva more. The same goes for all other types of calls.

For my invoices this makes about 1 to 1.5 leva each month on every invoice. I have 3 numbers and I have separate invoices fro them so about 4 to 6 leva every moth are taken extra by Mtel.

Now, Mtel proclaims it has about 2 million subscribers. If even 25% of them - about 500 000 are affected by this one, a rough estimate will go to about 0.5 million leva per moth of income due to 'technical error'.
Ysteday I tried calling a service representative, a man obviously without third grade education - he did not understood how I calculate 20% VAT by multiplying with 1.2 or how 0,004 makes a difference.

I am planing to loose a reasonable amount ot time with KZP (consumer protection commission) and CRC (communication regulatory commission) since the later had approved the rates and presumably the wrong counting method.
I will also take this to the country's ombudsman.