AM I BEING RIPPED OFF BY A GARAGE - Renault Grand Scenic?

If it doesn,t turn over it is either poor battery or starter bad earth etc.It sounds it is immoblised or poss crank sensor fault.As we go around garages fixing their ups it sounds like they are barking up the wrong tree.It is amazing how poor garages are at finding easy faults,but as we mend them all day,i mean faults they cannot find it is probably just we are more experienced with these faults.It is very unlikely it is camshaft sensor faults as except in early cars with hall effect senors for camshafts it would not stop it sparking or indeed turning over engine