Unauthorized worked performed and backing it with a lie

My vehicle was booked for a service and a problem was found. My warranty policy and number given and a claim submitted by KIA Wonderwaters . Im now struggling as the service adviser (Angelique) is saying that she Phoned me to say that the warranty is not going to pay for strip and assemble and that i instructed her to continues working on the problem and agreed to pay for 6hours on my account that ended up paying R5000 just on labor alone. This never happend and is the biggest lie I have ever heard. Who will let someone work on you account without asking what it is going to cost?