Boost Mobile LaVergne TN Jessica Deactivated my Upgrade LaVergne Tennessee

 I went into a boost Mobile store located on Murfreesboro Rd in LaVergne TN 2 weeks ago to upgrade to the iPhone 6 plus which I was eligible for at the time. The "manager" Jessica went through the whole process of switching my service to the new phone and when it was time to pay I handed her an AMEX card which was one of the acceptable payment methods as advertised on their front door upon entering. Anyhow, she then told me that she can not accept AMEX and to go next door to get cash. Their cash machine did not work and at that time I just decided that I will just wait until I am home in my town to go to the boost Mobile store that I usually go to. I had no idea that at that time I would be ineligible for an upgrade any longer since the " manager" failed to tell me. I called her and she totally blew me off as if it were my fault that "she" activated my phone before rejecting my payment that is clearly advertised on the front door as an acceptable payment method. She actually said there is nothing that she can do. She never offered to do anything to fix the problem and I am still ineligible for an upgrade due to no fault of my own but a lack of customer service. Since Jessica does not care to fix her mistake, who will fix it for her?