From Call centre to Finance director i cannot find a single fault. Bravo

So i moved into a new house, It has a drain in the back, A municipal drain. I thought i would call drain surgeon to come unblock it as there was toilet paper and human waste flooding my garden. They came out same day. I have no learnt that municipal drain are ******* to work on so drain sugeon left. But before they left they gave me step by step guide on what to do and eventually the municipality came out and unblocked it. (sameday). I recieved an invoice the very next day from Drain surgeon, when i called to say no work was done, I got an email from the finance director and his team stating they would credit the invoice to ZERO and he would waiver the call out fee as a gesture of goodwill because i didnt know the council needed to be called first. I will only use them if i have a personal drain blocked.