Attempted Oil Change

I took my car in a few months back to get the oil changed. Had a decent experience, it is close to my office so I was able to drop off my car and come back after work. I got the synthetic blend oil change for $20 and thought it was a great deal. I attempted to bring my car in again this morning and they told me that the $20 deal would not work for my car and I had to use the $50 full synthetic. I was extremely concerned because they either put the wrong oil in my car the first time or were trying to take advantage of me and get me to spend more money. Needless to say I did not leave my car there and will no longer use their services. The sad part is that it was the same service manager I dealt with the first time that told me the $20 deal would not work for my car. When I explained to him that I took it to him previously and was concerned that the wrong oil has been in my car for three months he shrugged his shoulders and said we will flush it out. It was absolutely ridiculous and I hope he does not feel that way with all services that they provide. Next time he may shrug his shoulders when they don't put the lug nuts on tight enough.