Firstly the disconnection fee is charged by BT and passed on by Plusnet only if YOU DON'T use a MAC. You are presumably switching to an unbundled line (llu) with HORRANGE so there are physical changes made at your exchange by BT engineers.HORRANGE(and almost all other ISPs) would charge you if you were moving from them under the same circumstances.
As to Customer Services - well in my humble opinion and experience Plusnet are infinitely better than HORRANGE !!
1. Their Customer Service centre is UK based; try dealing with Mumbai(or points East!) if you have either a technical or billing issue!!!!I've been there and its not good for the blood pressure or bank balance - just search for Orange problems if you don't believe me.
2. They have an active and extremely helpful public forum which is frequently visited by their Customer Care reps.
If you really have been treated rudely,I suggest you post your story on the Plusnet forum,I'm sure that you will get a polite reply!!