Engine over-revving .

My mother purchased a new Toyota Etios 1.5 XS in 2012 at Humansdorp Toyota, at first there was no problem with the engine over-revving but at some stage the engine started over-revving without her having her foot near the accelerator, she took it back about 4-5 times complaining about the problem, whilst the vehicle was still under warranty, they would do some tests and tell her that it is the floor carpet interfering with the pedal, meanwhile ,the carpet is fixed to the floor with clips, still it over-revved, she then got fed up with them, she then took it to Algoa Toyota, Newton Park, Port Elizabeth, same story and it still keeps on over-revving. She is visiting me now in Pretoria so she went to McCarthy Toyota Sinoville, same old story and then they claim that it is an Etios issue and will just happen again. Again they send her away with nothing being done at all. She has spoken to other Etios owners who have had the same problem and their vehicles computer was replaced. Now the warranty has expired and she will have to live with it as this large dealership just shrugs it's shoulders.