Kmeans Clustering of matrices

I have this matrix

x=[ 2+2*i 2-2*i -2+2*i -2-2*i];

i want to simulate transmitting it and adding a noise to it. I represented the components of the complex number as below:

A=randn(150,2)+2*ones(150,2); C=randn(150,2)-2*ones(150,2);

At the receiver i received the below vector, where the components are ordered based on what i sent originally (i.e. the components of x).

X = [A A A C C A C C];

Now i want to apply the kmeans(X) to have 4 clusters, so kmeans(X,4). I am having the below problems:

1. I am not sure if i can represent the complex numbers as shown in X above.
2. I cannot plot the result of the kmeans to show the clusters.
3. I could not understand the clusters centroid results.
4. How can i find the bet error rate, if this example was to represent a communication system and at the receiver the k-means clustering was used in order to decide for what the transmitted signal was?

Thank you for your fast response.

Kawther Hamad