Metro PCS Advertised AS PRE PAID CELL SERVICE, BUT RIPPED ME OFF !! Richardson Texas

I have had service with Metro PCS for almost a year. It's a pre paid phone service that is due monthly, in advance , the amount of the plan you selected. Because my income is limited, many times my service has been disconnected. If your service is disconnected for 30 days. Your account is closed and you must open a new account to regain service, which requires you are assigned a new number. In the past, I have always made the monthly payment to reconnect service within the 30 days time limit. Therefore my cell number has remained the same. I have been required to pay a 5.00 service charge so the due date for my account could be adjusted , so the next payment due would provide the 30 days of service I paid in advance. Yesterday, by credit card on the phone, I paid my balance in full and the 5.00 late charge required to adjust the payment date. My cell account status stated I would owe another full monthly payment on the 29th, 6 days from paying for a months service. I called customer service , spoke with a superviser and was told that my payment due date could not be change, I would only recieve 6 days of service for a full month payment!!!! This has not been the practice in the past. My cell has been discopnnected many times and the due date adjusted so that I would get my full months service for my monthly payment. Not only have they taken the 5.00 extra for late charge and to adjust the due date. They are cheating me of over 3 weeks of service I paid for in advance. PLEASE HELP ME!!!!! I can't find any contact information for Corporate Headquarters and am not allowed access to my account online. Too make sure I had my sign in infomration correct, I accessed the sign in help link and recieved an email with the user name and password but still can't access my account!!!!