Did they actually do anything to find the problem?

Brought our hob in for assessment. They said nothing was wrong. I paid the R250 service fee. Our electrician came to install the hob only to find some electronics fried and also infested with roaches. Claremont Home Aplliances says they didnt have to open the unit because it worked when they plugged it in. Lets think about this. Why did I disconnect and bring in the hob? I brought in the hob because it doesnt work and I needed them to find the reason why it does not work at my house after 4years of use. That's why I paid a non-refundable fee charge. They said nothing was wrong with the hob. Upon mention about the found roaches, they then said I must get the roach infestation clearance certificate done before i bring it in again because they dont clean the units of infestation. I didnt know about the infestation and believe this is part of the problem to the faulty unit. If they did their job, this would have been picked up and they would bot have phoned me to say nothing is wrong with the hob. Plenty of wrong to the unit if you ask me showing they are not thorough in their work.