They knew a bribe would be paid and why they came after office hours when their call center is closed for the day.
What do you mean the call center is closed after office hours? Wtf? A call center is for emergency and has to be 24/7! What kind of crooked world is that?
Billing enquiries via the call center are all operated on office hours. If you have a fault or problem for electricity they are "open" but does not mean they will fix it immediately. I normally see area faults via twitter and they are in the hundreds.
You live in the wrong country. Most of the African countries are going backwards. Things are getting worse and in 10 or 20 years they are back in stone age.