I have taken the storm ready wifi to the xfinity store and returned it to the staff, when will I be able to get my refund！！！

Today I have taken the storm ready wifi to the xfinity store and returned it to the staff, when will I be able to get my refund. The staff seemed to complete an application for me on the computer and gave me a ticket number, and then less than a moment later I received a message that the ticket had been closed. I asked the staff and they told me that the refund had been completed. I asked the staff several times to make sure they had successfully returned the machine for me. They promised me that my bill would be updated and the refund would be immediate or maybe on the next bill. They promised me so I had to choose to believe it, but I was still worried because I saw that the estimated amount of my next bill included the full price of this storm ready wifi, which was more than three hundred dollars! What is going on? I was simply signing up for an internet plan and the store staff insisted on giving me this storm ready wifi without telling me I was going to buy it, just telling me I needed it for my internet plan. I didn't need it at all and I returned it to them as soon as I realized the problem. I think this is a deceptive behavior！！！And now the staff has taken away my storm ready wifi and told me that it has been returned, why are you still charging me the full price of the storm ready wifi. This is abominable and unbelievable!!! You [Edit: Inflammatory]!!! You guys need to help me fix this by correcting my bill ASAP! Otherwise I will pursue legal responsibility against you!!!