Student Finance - NI Number

So I've been waiting for my national insurance number to come by post since around 20th june. Currently I only have a temporary NI number. I've contacted HMRC several times and I've been told letters have been sent out, the first letter they sent out was sent to the wrong address on the 1st of july, the second letter was due on the 18th and didn't actually arrive. I am really unsure what to do now at this point.