It seems there are two issues here.
Firstly you were sold an apparently inappropriate machine with extras you didn't need/want!
Also you have a faulty unit.
At this stage I would think the most important aspect is to get you up and running properly.
The mis-selling you will probably have to put down to experience.
In the first instance I would make a list of your specific problems and the actions that have been taken and go into the store and demand to be able to talk to the manager.
Hopefully he will be able to come up with a compromise solution.
There are many other options available to you but they will all take time and, it seems to me, you just want to get fully operational again as quickly as possible.