The most horrible service

I called the shop on Thursday, gave my car information including the VIN number, I was given a reference code, went and bought a part on Friday, I insisted that the collection side confirmes that the part is for a golf 6, 1.6 Trendline, he has it was correct. When I got to the machenic it was wrong, today I return the part with a sample so they can exchange it, I forgot my wallet at home, they needed the slip, they called home asked them to take a picture of the slip for the sake of progress, also as per the manager’s instructions, to my surprise I still couldn’t be assisted. What made me more mad was the deliberation between different managers, making me wait for over 20 minutes only to tell me that they want the original slip. The most unprofessional ran business I have ever seen.