It's probably the OutCasts. They're allies of the Lane Hackers and you won't be able to dock with Mactan if they're hostile to you.
Once you hit level 10 you can start ignoring the calls to take story missions and do some exploring up in the northern border worlds. Stop at every freeport and eventually you'll find somebody to fix you up with the Outcasts. (also makes travel in the northern systems much easier) This will also raise your rep with the Hackers and lower it with police and military.
Once you're OK with the Hackers and the Outcasts you should be able to dock at Mactan and buy your ship.
That's a great ship. It got me through most of the single player game and went to most of the systems in the game. Hated when I had to trade down to a fighter.
If you want to make lots of cash while you're exploring, detour into Kusari space and pick up a Drone freighter. When you find a big money run the 175 cargo will really pay off.
SMS...