Do they know how to do their jobs?

On the 3rd of Feb I paid my account via the website. Afterwards I get my invoice for the next month showing that my account has not been settled, cellphone gets disconnected, phone them to get it sorted, they tell me to email proof of payment which I did. Couple of days later and my phone is still disconnected, phone again, get told again to send through proof of payment, do this again to three people within the company. Get an email back stating that the line has been reconnected, but my account still has not been fixed and the payment allocation still has not been made. Receive a phone call this morning from the collections department that I need to settle my account, tell them that I have settled the account on the 3rd already and lo and behold I need to send proof of payment again. Please can someone explain to me, how do they not pick it up when the payment was done through their own website, 4 emails have been sent with the proof of payment and yet no one seems to be able to fix the problem?