straight talk sent defective phone ocala, Internet

I ordered a cell phone from straighttalk.com  I ported my number over and went to use my brand new phone.  My new phone shuts off by itself every minute or so.  It is impossible to do anything on it.  I have contacted customer service and was told I will ship the phone to them and they will ship me a new one.  This means I will be without a phone for a few weeks.  I said I would prefer to just return the phone, go to walmart and get a new one so that way I will not be without a phone.  I was told that if I choose to do that I will have to pay for shipping myself.  I asked if there was any other way that I could get a replacement phone since I have health problems and cannot be without a phone.  I was told no.