Wizards Hair & Beauty Studio Unclaimed

This is the second time this happened to me at this hair salon. Upon purchasing a brazilian blowout service, one is not provided with honest consultation about the additional costs involved. Only after the service has been performed on my hair, was I informed that I in fact needed to purchase hundreds of rands worth of products to allegedly maintain the brazilian treatment. Upon payment an indemnity was shoved in front me, with no explanation whatsoever, which I was expected to sign. The document states that Wizards is not responsible for the outcome of the service they offered unless I use stipulated products. Why is this agreement, and information about the required products, not presented to clients BEFORE the purchase the service? Now, if I cannot afford the products they want to sell me, that means the service I have already received, and have to pay R650 for, will go to waste - hence my allegation of dishonest conduct.