Need to upgread the cable without changing wall cable

Hello,my apt has old cable and their not planning to up grade what can i do on my end between cable and hgtv to get the hd channels

Is the cable from a cable company? Or a master antenna? If there is a cable company, they can lease you an HDTV cable box. If there is an antenna that is shared by the apartments, there is really nothing you can add to receive HDTV.
Sometimes, if the apartment is facing the right direction, you can install a small satellite dish. If you have internet with decent speed, you can watch some HD programs over the internet. This depends on how good your computer is also. With an up to date computer, the computer can feed video to the TV set, and you can watch some HD programs. A computer with HD capability can cost some $$$.
Hopefully, you have cable TV, from a cable company, which is the easiest way- you can rent the HDTV box for about $5 a month more.