Failed treatment, without the advertised recourse

My brazilian hair treatment at Sorbet Dunkeld failed - not only in my view but also the professional hairdresser that I consulted afterwards. The Sorbet website promises if they "can’t turn that frown back into a smile, then your treatment is on us", but of course in reality neither the group nor the owner of the particular franchise is willing to deliver on this promise. I will never visit Sorbet again, not only because of the particular (expensive) disappointment, but also because they don't take responsibility if something goes wrong.