Assurance Wireless review: Phone

I just recieved my phone today in the mail and after setting it up and I used it for about an half hour it cut off on me and now it just keeps cutting off and on and not even getting to the home screen. I feel that is is a default phone which this happen to me before with this same company so i dont know what yal have going on but I would like a new phone.
model: SP555D imei#990018256943451