DIRECTV is starting to play hardball with obsolete packages. You're going to have to do battle over the phone and they may well tell you that you cannot order HBO without updating your package choice.
I didn't even have to talk to a human, just used the phone to add HBO via the automated system, and verified on line still on grandfathered package.aa9vi said:Just call on the phone (speak to an actual human being) and ask them to add on HBO. I had a similar issue with another movie pack. I called and it was no problem. I didn't have to upgrade to a current base pack, either.