After that last year at a turn extra work had been...

After that last year at a turn extra work had been carried out without consultation and the bill was therefore about 60% higher than agreed last week, my polo brought back for a turn.
I was looking for another garage myself, but my wife still thought I should try it once.
Appointment was a big turn and rental car but later I canceled the rental car because my neighbor brought me.
Upon issuing the car notice that the turn would cost around 650 euros instead of 330 euros because filters and spark plugs had to be replaced was the advice.
My car just 4 years old and 35000 km driven I have also partly on advice neighbor the spark plugs not replaced, but the filters what came to 45 euros.When retrieving I asked how they came to 300 euros for 4 spark plugs while importer says extra work of 130 euros?
They did not know the answer either, as was agreed when making an appointment, nothing was agreed.
They didn't know it either, very sloppy and luckily this time my neighbor witnessed it.
If you are not alert, they will earn a lot from you, missed opportunity.