I'm no expert but would have thought the old lawn should have been taken up. rather than rotovated into the ground.
The problem with getting someone into to lay a lawn if you know little about lawn laying or don't have anyone to advise you and I don't mean this in a disrepectful way, unless you get a number of quotes and ask questions then you take your chances.
My lawn was laid a few years ago but the old one was uneven and riddled with dandilions and even friends with no gardening knowledge pointed out that the old needed to be taken up other wise the dandilions would grow through.
I rang a few different places to lay turf after the ground had been prepared and only one would come and put turf down on ground they had not prepared or seen before but said they needed to see the soil before laying and would say no if they didn't like the prep.
The guy's who laid it told me dandilions were likely to grow back and in one area the grass would not grow very well but provided good advise as to what to do.
Name and shame the company...