Felt like I was a bother

I passed through the pharmacy yesterday (my preferred pharmacy). However I was not happy with the service I received from Zanele Makhanya. I greeted her but she was not cheerful to me and appeared grumpy and uninterested. After I had finished paying and was still putting away my card, she called next to the white gentleman behind me and she greeted him in a cheerful manner and asked him how his day was. This was unlike the service she gave me where it appeared as if I was being a bother. Could it be because I am a black woman have anything to do with it? I will avoid her till point next time as i was so annoyed by this treatment